Mask blank substrate, substrate with multilayer reflection film, transmissive mask blank, reflective mask, and semiconductor device fabrication method

ABSTRACT

Disclosed is a mask blank substrate for use in lithography, wherein the main surface on which the transfer pattern of the substrate is formed has a root mean square roughness (Rms) of not more than 0.15 nm obtained by measuring an area of 1 μm×1 μm with an atomic force microscope, and has a power spectrum density of not more than 10 nm 4  at a spatial frequency of not less than 1 μm −1 .

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Continuation of application Ser. No. 14/348,413, filed Mar.28, 2014, claiming priority based on International Application No.PCT/JP2013/059199 filed Mar. 28, 2013, claiming priority based onJapanese Patent Application No. 2012-074626 filed Mar. 28, 2012, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a mask blank substrate, a substratewith a multilayer reflective film, a transmissive mask blank, areflective mask blank, a transmissive mask, a reflective mask, and amethod of manufacturing a semiconductor device, which ensure suppressionof false defects (pseudo defects, nuisance defects) originating from thesurface roughness of a substrate and a film in defect inspection using adefect inspection apparatus of a high sensitivity, and facilitate thedetection of critical defects such as foreign matters and scratches.

BACKGROUND ART

Generally, in the process of manufacturing a semiconductor device, finepatterns are formed using photolithography. A number of transfer maskscalled photomasks are normally used in forming the fine patterns. Thistransfer mask is generally a fine pattern formed by a metal thin film orthe like and provided on a transparent glass substrate, andphotolithography is also used in the fabrication of the transfer mask.

A mask blank having a thin film (e.g., a light shielding film (an opaquefilm)) for forming a transfer pattern (a mask pattern) on a transparentsubstrate such as a glass substrate is used in fabricating the transfermask by photolithography. The fabrication of the transfer mask using themask blank involves a drawing process of drawing a desired pattern on aresist film formed on the mask blank, a developing process of developingthe resist film after drawing to form a desired resist pattern, anetching process of etching the thin film as a mask, and a process ofstripping and removing the remaining resist pattern with the resistpattern used as a mask. In the developing process, after the desiredpattern is drawn on the resist film formed on the mask blank, adeveloper is supplied to the resist film to dissolve a portion of theresist film which is soluble in the developer, thereby forming theresist pattern. In the etching step, with the resist pattern used as amask, an exposed portion of the thin film where the resist pattern isnot formed is removed by wet etching or dry etching, thereby forming adesired mask pattern on the transparent substrate. The transfer mask isfinished in this way.

A phase shift mask, as well as a binary mask having a light shieldingpattern of a chromium-based material on a conventional transparentsubstrate, is known as the types of a transfer mask. The phase shiftmask is configured to have a phase shift film on a transparentsubstrate. The phase shift film has a predetermined phase difference,and is made of, for example, a material containing molybdenum silicidecompound. Further, a binary mask using a material containing a silicidecompound of a metal such as molybdenum for a light shielding film isbeing used. These binary mask and phase shift mask are generally calleda transmissive mask herein, and a binary mask blank and a phase shiftmask blank, which are used as a master for a transfer mask, aregenerally called a transmissive mask blank herein.

In recent years, higher integration of semiconductor devices in thesemiconductor industry requires fine patterns beyond the transfer limitof the conventional photolithography using ultraviolet light. To enableformation of such fine patterns, EUV lithography which is an exposuretechnique using extreme ultraviolet (hereafter referred to as “EUV”) ispromising. EUV light refers to light in the waveband of the soft X-rayregion or the vacuum ultraviolet region, specifically, light with awavelength of about 0.2 to 100 nm. A reflective mask has been proposedas a transfer mask for use in the EUV lithography. Such a reflectivemask has a multilayer reflective film formed on a substrate to reflectexposure light, and an absorber film patterned on the multilayerreflective film to absorb exposure light.

The reflective mask is fabricated by forming an absorber film patternusing photolithography from the reflective mask blank including asubstrate, a multilayer reflective film formed on the substrate, and anabsorber film formed on the multilayer reflective film.

As described above, as a demand for miniaturization in the lithographyprocess increases, problems in the lithography process are becomingprominent. One of the problems concerns defect information on a maskblank substrate and a substrate with a multilayer reflective film, whichare used in the lithography process.

The mask blank substrate is demanded to have a higher flatness from theviewpoints of an improvement on the defect quality needed with therecent miniaturization of patterns and the optical characteristicsneeded for transfer masks. The conventional surface processing methodsfor mask blank substrates are described in, for example, PatentLiteratures 1 to 3.

Patent Literature 1 describes a glass-substrate polishing method ofpolishing the surface of a glass substrate essentially comprising SiO₂by using a polishing slurry containing colloidal silica with an averageprimary particle size of 50 nm or less, acid, and water, and adjusted tohave a pH of 0.5 to 4, in such a way that the surface roughness, Rms, asmeasured with an atomic force microscope becomes not more than 0.15 nm.

Patent Literature 2 describes a polishing agent for the synthetic quartzglass substrate, which contains a suppressive colloidal solution and anacidic amino acid to suppress the formation of defects to be detected bya high-sensitivity defect inspection apparatus on the surface of asynthetic quartz glass substrate.

Patent Literature 3 describes a method of controlling the flatness of aquartz glass substrate by placing the quartz glass substrate in ahydrogen radical etching apparatus, and causing hydrogen radicals to actwith the quartz glass substrate, so that the flatness can be controlledin the sub-nanometer order.

The substrate with a multilayer reflective film is also demanded to havea higher flatness from the viewpoints of an improvement on the defectquality needed with the recent miniaturization of patterns and theoptical characteristics needed for transfer masks. The multilayerreflective film is formed by alternately laminating a high refractiveindex layer and a low refractive index layer on the surface of the maskblank substrate. Those layers are generally formed by sputtering usingsputtering targets made of materials for forming the layers.

As a method of sputtering, ion beam sputtering is preferably carriedout, it is because it does not need produce a plasma through discharge,making it difficult to mix an impurity in the multilayer reflectivefilm, and has an independent ion source so that the conditions are setrelatively easily. In view of the smoothness and surface uniformity ofeach layer to be formed, sputter particles are reached the main surfaceof the mask blank substrate at a large angle to the normal line of themain surface of the mask blank substrate (line perpendicular to the mainsurface), i.e., at an angle oblique to or nearly parallel to the mainsurface of the substrate to deposit a high refractive index layer and alow refractive index layer.

As a technique of manufacturing a substrate with a multilayer reflectivefilm with this way, Patent Literature 4 describes that at the time ofdeposing a multilayer reflective film for a reflective mask blank forEUV lithography on a substrate, ion beam sputtering is carried out bykeeping the absolute value of an angle α defined by the normal line ofthe substrate and the sputtered particles incident to the substrate at35°≤α≤80° while rotating the substrate about the central axis of thesubstrate.

-   Patent Literature 1: JP-A-2006-35413-   Patent Literature 2: JP-A-2009-297814-   Patent Literature 3: JP-A-2008-94649-   Patent Literature 4: Unexamined Japanese Patent Application    Publication (Published Japanese Translation of PCT Application)    JP-A-2009-510711

With the rapid miniaturization of patterns in lithography using an ArFexcimer laser or EUV (Extreme Ultra-Violet), the defect sizes oftransmissive masks (also called optical masks), such as a binary maskand a phase shift mask, and an EUV mask that is a reflective mask, arealso becoming smaller. To find such fine defects, the wavelength of theinspection light source used in defect inspection is approaching thelight source wavelength of the exposure light.

For example, as a defect inspection apparatus for an optical mask, amask blank, which is a master thereof, and a substrate, high-sensitivitydefect inspection apparatuses with an inspection light source wavelengthof 193 nm are becoming popular. As an EUV mask, an EUV mask blank, whichis a master of an EUV mask, and a substrate, high-sensitivity defectinspection apparatuses with inspection light source wavelengths of 266nm (for example, the mask substrate/blank defect inspection apparatus“MAGICS M7360” for EUV exposure of Lasertec Corp.), of 193 nm (EUVmask/blank defect inspection apparatus “Teron 600 series” of KLA-TencorCorp.), and of 13.5 nm are becoming popular.

The main surface of a substrate used for the conventional transfer maskis managed by surface roughness represented by Rms (root mean squareroughness) and Rmax (maximum height) in the fabrication process. Becausethe detection sensitivity of the high-sensitivity defect inspectionapparatus described above is high, however, many false defects aredetected in defect inspection of the main surface of the substrate evenwhen the smoothness in compliance with Rms and Rmax becomes higher fromthe viewpoint of the improvement on the defect quality, raising aproblem such that the defect inspection cannot be performed to the end.

Further, an attempt is made to deposit the multilayer reflective film ofthe substrate with a multilayer reflective film used in the conventionaltransfer mask by, for example, the method described in “Background Art”to reduce recess defects present on the substrate. Even if defectsoriginating from the recess defects on the substrate can be reduced,defect inspection on the multilayer reflective film raises a problemsuch that many defects are detected (the number of defectsdetected=critical defects+false defects) because the detectionsensitivity of the high-sensitivity defect inspection apparatusdescribed above is high.

The false defect mentioned herein refers to a tolerable irregularity onthe substrate surface or the multilayer reflective film, which does notaffect pattern transfer, and which is erroneously determined as a defectin inspection with a high-sensitivity defect inspection apparatus. Whena lot of such false defects are detected in defect inspection, criticaldefects that affect pattern transfer may be buried in many falsedefects, so that the critical defects cannot be discovered. For example,a defect inspection apparatus having an inspection light sourcewavelength of 266 nm, 193 nm or 13.5 nm, which is currently becomingpopular, cannot inspect the presence or absence of critical defects fora substrate or a substrate with a multilayer reflective film having asize of, for example, 132 mm×132 mm, because the number of detecteddefects exceeds 100,000. Overlooking critical defects in defectinspection would cause failures in the later mass production process ofsemiconductor devices, leading to wasteful labor and economical loss.

DISCLOSURE OF THE INVENTION

The present invention has been made in consideration of theaforementioned problems, and it is an object of the invention to providea mask blank substrate, a substrate with a multilayer reflective film, atransmissive mask blank, a reflective mask blank, a transmissive mask, areflective mask, and a method of manufacturing a semiconductor device,which ensure suppression of false defects originating from the surfaceroughness of a substrate and a film in defect inspection using a defectinspection apparatus of a high sensitivity, and facilitate the detectionof critical defects such as foreign matters and scratches.

Further, it is another object of the invention to provide a substratewith a multilayer reflective film, which has fewer defects includingfalse defects to be detected even by a high-sensitivity defectinspection apparatus using lights with various wavelengths, achievessmoothness required particularly for a substrate with a multilayerreflective film, and, at the same time, permits critical defects to bereliably detected because of fewer detected defects including falsedefects, a method of manufacturing the substrate with a multilayerreflective film, a reflective mask blank obtained by using thesubstrate, a method of manufacturing the reflective mask blank, areflective mask and a method of manufacturing the same, and a method ofmanufacturing a semiconductor device.

The present inventors have made intensive studies to solve the aboveproblems, and have discovered that the roughness of the component of apredetermined spatial frequency (or spatial wavelength) affects theinspection light source wavelength of a high-sensitivity defectinspection apparatus. Accordingly, the spatial frequency of thatroughness component among the roughness (unevenness) components on themain surface of a substrate or a film (for example, multilayerreflective film) which is erroneously determined as a false defect isspecified, and the amplitude intensity at this spatial frequency ismanaged to enable suppression of detection of false defects and makecritical defects noticeable in defect inspection.

In addition, while some attempts have been made to reduce the surfaceroughness of a multilayer reflective film of a substrate with amultilayer reflective film from the viewpoints of the reflectancecharacteristics of the multilayer reflective film, the relation of thesurface roughness with detection of false defects by a high-sensitivitydefect inspection apparatus, has not been known.

To achieve the objects, a mask blank substrate for use in lithographyaccording to an exemplary embodiment of the invention is configured sothat the main surface on which the transfer pattern of the substrate isformed has a root mean square roughness (Rms) of not more than 0.15 nmobtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, and has a power spectrum density of not more than 10 nm⁴ ata spatial frequency of not less than 1 μm⁻¹.

To achieve the objects, a substrate with a multilayer reflective filmaccording to an exemplary embodiment of the invention is configured tocomprise a multilayer reflective film having a high refractive indexlayer and a low refractive index layer alternately laminated on thesurface of the aforementioned mask blank substrate of the invention.

To achieve the objects, a substrate with a multilayer reflective filmaccording to an exemplary embodiment of the invention is configured tocomprise a multilayer reflective film having a high refractive indexlayer and a low refractive index layer alternately laminated on a mainsurface of a mask blank substrate for use in lithography, wherein asurface of the multilayer-reflective-film formed substrate has a rootmean square roughness (Rms) of not more than 0.15 nm, obtained bymeasuring an area of 1 μm×1 μm with an atomic force microscope, and hasa power spectrum density of not more than 20 nm⁴ at a spatial frequencyof not less than 1 μm⁻¹.

To achieve the objects, a transmissive mask blank according to anexemplary embodiment of the invention is configured to comprise a lightshielding function film to be a transfer pattern on the main surface ofthe aforementioned mask blank substrate of the invention.

To achieve the objects, a reflective mask blank according to anexemplary embodiment of the invention is configured to comprise anabsorber film to be a transfer pattern on the multilayer reflective filmor the protective film of the aforementioned substrate with a multilayerreflective film of the invention.

To achieve the objects, a transmissive mask according to an exemplaryembodiment of the invention is configured to comprise a light shieldingfunction film pattern provided on the main surface by patterning thelight shielding function film of the aforementioned transmissive maskblank of the invention.

To achieve the objects, a reflective mask according to an exemplaryembodiment of the invention is configured to comprise an absorberpattern provided on the multilayer reflective film by patterning theabsorber film of the aforementioned reflective mask blank of theinvention.

To achieve the objects, a method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the invention is configured tocomprise a step of forming a transfer pattern on a transferred substrateusing the aforementioned transmissive mask of the invention byperforming a lithography process using an exposure device.

To achieve the objects, a method of manufacturing a semiconductor deviceaccording to an exemplary embodiment of the invention is configured tocomprise a step of forming a transfer pattern on a transferred substrateusing the aforementioned reflective mask of the invention by performinga lithography process using an exposure device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a perspective view illustrating a mask blank substrate 10according to an exemplary embodiment of the present invention. FIG. 1(b)is a schematic cross-sectional view illustrating the mask blanksubstrate 10 of the present embodiment.

FIG. 2 is a schematic cross-sectional view illustrating an example ofthe configuration of a substrate with a multilayer reflective filmaccording to an exemplary embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating an example ofthe configuration of a reflective mask blank according to an exemplaryembodiment of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating an example of areflective mask according to an exemplary embodiment of the presentinvention.

FIG. 5 is a schematic cross-sectional view illustrating an example ofthe configuration of a transmissive mask blank according to an exemplaryembodiment of the present invention.

FIG. 6 is a schematic cross-sectional view illustrating an example of atransmissive mask according to an exemplary embodiment of the presentinvention.

FIG. 7 is a graph illustrating the results of power spectral analysis ofthe main surfaces of the mask blank substrates according to Examples 1to 4 of the present invention and Comparative Examples 1 and 2.

FIG. 8 is a graph obtained by extracting the results of the powerspectral analysis of the main surfaces of the mask blank substrates ofExamples 1 to 4 of the present invention in FIG. 7.

FIG. 9 is a graph obtained by extracting the results of the powerspectral analysis of the main surfaces of the mask blank substrates ofComparative Examples 1 and 2 in FIG. 7.

FIG. 10 is a graph illustrating the results of power spectral analysisof the main surface of the mask blank substrate of Example 5 of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

General Description

To achieve the above-described objects, the present invention has thefollowing configurations.

(First Configuration)

A first configuration of the present invention is a mask blank substratefor use in lithography, wherein the main surface on which the transferpattern of the substrate is formed has a root mean square roughness(Rms) of not more than 0.15 nm obtained by measuring an area of 1 μm×1μm with an atomic force microscope, and has a power spectrum density ofnot more than 10 nm⁴ at a spatial frequency of not less than 1 μm⁻¹.

According to the first configuration, the main surface of the mask blanksubstrate is configured in such a way that the power spectrum density,which is the amplitude intensity of all roughness components detectablein an area of 1 μm×1 μm, at a spatial frequency of not less than 1 μm⁻¹,is set to not more than 10 nm⁴, making it possible to suppress detectionof false defects in the defect inspection using a high-sensitivitydefect inspection apparatus, thereby making the critical defects morenoticeable.

(Second Configuration)

A second configuration of the invention is a mask blank substrateaccording to the first configuration, wherein the main surface has apower spectrum density of not more than 10 nm⁴, obtained by measuring anarea of 1 μm×1 μm with an atomic force microscope, at a spatialfrequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹.

According to the second configuration, it is possible to significantlysuppress detection of false defects in the defect inspection using ahigh-sensitivity defect inspection apparatus with inspection light inthe wavelength range of 150 nm to 365 nm, e.g., a UV laser with aninspection light source wavelength of 266 nm or an ArF excimer laserwith an inspection light source wavelength of 193 nm, thereby making thecritical defects more noticeable.

(Third Configuration)

A third configuration of the invention is a mask blank substrateaccording to the second configuration, wherein the main surface has apower spectrum density of not less than 1 nm⁴ and not more than 10 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹.

According to the third configuration, reducing the power spectrumdensity to 1 nm⁴ makes it possible to sufficiently suppress detection offalse defects in the defect inspection using a high-sensitivity defectinspection apparatus with inspection light in the wavelength range of150 nm to 365 nm, e.g., a UV laser with an inspection light sourcewavelength of 266 nm or an ArF excimer laser with an inspection lightsource wavelength of 193 nm, thereby making the critical defects morenoticeable. Therefore, it is not necessary to form the main surface inan extremely smooth and highly precise surface state, so that the loadof the process of manufacturing the mask blank substrate can bedecreased.

(Fourth Configuration)

A fourth configuration of the invention is a mask blank substrateaccording to any one of the first to third configurations, wherein themain surface is subjected to a surface treatment with catalyst-referredetching.

According to the fourth configuration, because the main surface isselectively subjected to a surface treatment from convex portionscontacting the surface of the catalyst which is a reference surface bycatalyst-referred etching, irregularities (surface roughness) formingthe main surface become highly aligned surface states while being keptvery smooth, and become such surface states that the ratio of concaveportions is greater than the ratio of convex portions with respect tothe reference surface. When a plurality of thin films are laminated onthe main surface, the size of defects on the main surface tend to becomesmaller, which is preferable from the viewpoint of the defect quality.Particularly, the effect is demonstrated when a multilayer reflectivefilm to be described later is formed on the main surface. Further,execution of a surface treatment to the main surface bycatalyst-referred etching as mentioned above makes it possible torelatively easily form the surface with the surface roughness and thepower spectrum density as defined in the first to third configurations.

(Fifth Configuration)

A fifth configuration of the invention is a mask blank substrateaccording to any one of the first to fourth configurations, wherein themask blank substrate is used in EUV lithography.

According to the fifth configuration, the substrate is a mask blanksubstrate for use in EUV lithography, whereby the surface state of themultilayer reflective film formed on the main surface becomes verysmooth, so that the reflectance characteristics to EUV light becomebetter.

(Sixth Configuration)

A sixth configuration of the invention is a mask blank substrateaccording to the fifth configuration, wherein a thin film of a materialcomprising a metal, an alloy, or at least one of oxygen, nitrogen andcarbon contained in one of the metal and the alloy, is formed on themain surface of a substrate of multi-element glass.

Generally, since a mask blank substrate for use in EUV lithography needsthe characteristics of low thermal expansion, so that it is preferred touse a multi-element glass material to be described later. Themulti-element glass material has a property such that high smoothness isdifficult to obtain compared to synthetic quartz glass. Accordingly, athin film of a material comprising a metal, an alloy, or at least one ofoxygen, nitrogen and carbon contained in one of the metal and the alloyis formed on the main surface of the substrate comprising amulti-element glass material. Substrates having the surface states asdefined by the first to fifth configurations are easily obtained byperforming a surface treatment to the surface of such a thin film.

(Seventh Configuration)

A seventh configuration of the invention is a substrate with amultilayer reflective film comprising a multilayer reflective filmhaving a high refractive index layer and a low refractive index layeralternately laminated on the surface of the mask blank substrateaccording to any one of the first to sixth configurations.

According to the seventh configuration, the surface state of themultilayer reflective film formed on the main surface becomes verysmooth, so that the reflectance characteristics to EUV light becomebetter. The substrate with a multilayer reflective film can suppressdetection of false defects in the defect inspection of the surface ofthe multilayer reflective film using a high-sensitivity defectinspection apparatus, and further make the critical defects morenoticeable. In addition, it is possible to significantly suppressdetection of false defects in the defect inspection using ahigh-sensitivity defect inspection apparatus with inspection light inthe wavelength range of 150 nm to 365 nm, e.g., a UV laser with aninspection light source wavelength of 266 nm or an ArF excimer laserwith an inspection light source wavelength of 193 nm, or ahigh-sensitivity defect inspection apparatus with inspection light (EUVlight) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm.

(Eighth Configuration)

An eighth configuration of the invention is a substrate with amultilayer reflective film according to the seventh configuration,wherein the substrate with a multilayer reflective film has a protectivefilm on the multilayer reflective film.

According to the eighth configuration, the substrate with a multilayerreflective film has the protective film on the multilayer reflectivefilm to suppress damages to the multilayer reflective film at the timeof fabricating a transfer mask (EUV mask), so that the reflectancecharacteristics to EUV light become better. The substrate with amultilayer reflective film makes it possible to suppress detection offalse defects in the defect inspection of the surface of the protectivefilm using a high-sensitivity defect inspection apparatus, and furthermake the critical defects more noticeable. In addition, it is possibleto significantly suppress detection of false defects in the defectinspection using a high-sensitivity defect inspection apparatus withinspection light in the wavelength range of 150 nm to 365 nm, e.g., a UVlaser with an inspection light source wavelength of 266 nm or an ArFexcimer laser with an inspection light source wavelength of 193 nm, or ahigh-sensitivity defect inspection apparatus with inspection light (EUVlight) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm.

(Ninth Configuration)

A ninth configuration of the invention is a substrate with a multilayerreflective film according to the seventh or eighth configuration,wherein the surface of the multilayer reflective film or the protectivefilm of the substrate with a multilayer reflective film has a powerspectrum density of not more than 20 nm⁴, obtained by measuring an areaof 1 μm×1 μm with an atomic force microscope, at a spatial frequency ofnot less than 1 μm⁻¹.

According to the ninth configuration, the surface of the multilayerreflective film or the protective film has a power spectrum density ofnot more than 20 nm⁴, obtained by measuring an area of 1 μm×1 μm with anatomic force microscope, at a spatial frequency of not less than 1 μm⁻¹,making it possible to suppress detection of false defects in the defectinspection of the surface of the multilayer reflective film using ahigh-sensitivity defect inspection apparatus, and further make thecritical defects more noticeable. In addition, it is possible tosignificantly suppress detection of false defects in the defectinspection using a high-sensitivity defect inspection apparatus withinspection light in the wavelength range of 150 nm to 365 nm, e.g., a UVlaser with an inspection light source wavelength of 266 nm or an ArFexcimer laser with an inspection light source wavelength of 193 nm, or ahigh-sensitivity defect inspection apparatus with inspection light (EUVlight) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm.

(Tenth Configuration)

A tenth configuration of the invention is a substrate with a multilayerreflective film according to the ninth configuration, wherein thesurface of the multilayer reflective film or the protective film of thesubstrate with a multilayer reflective film has a power spectrum densityof not more than 20 nm⁴, obtained by measuring an area of 1 μm×1 μm withan atomic force microscope, at a spatial frequency of not less than 1μm⁻¹ and not more than 10 μm⁻¹.

According to the tenth configuration, it is possible to significantlysuppress detection of false defects in the defect inspection of thesubstrate with a multilayer reflective film using a high-sensitivitydefect inspection apparatus with inspection light in the wavelengthrange of 150 nm to 365 nm, e.g., a UV laser with an inspection lightsource wavelength of 266 nm or an ArF excimer laser with an inspectionlight source wavelength of 193 nm, thereby making the critical defectsmore noticeable.

(Eleventh Configuration)

An eleventh configuration of the invention is a substrate with amultilayer reflective film according to the ninth configuration, whereinthe surface of the multilayer reflective film or the protective film ofthe substrate with a multilayer reflective film has a power spectrumdensity of not more than 9 nm⁴, obtained by measuring an area of 1 μm×1μm with an atomic force microscope, at a spatial frequency of not lessthan 10 μm⁻¹ and not more than 100 μm⁻¹.

According to the eleventh configuration, it is possible to significantlysuppress detection of false defects in the defect inspection using ahigh-sensitivity defect inspection apparatus with inspection light (EUVlight) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm, thereby making thecritical defects more noticeable.

(Twelfth Configuration)

A twelfth configuration of the invention is a substrate with amultilayer reflective film according to any one of the ninth to eleventhconfigurations, wherein the surface of the multilayer reflective film orthe protective film of the substrate with a multilayer reflective filmhas a root mean square roughness (Rms) of not more than 0.15 nm,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope.

According to the twelfth configuration, it is possible to make thereflectance characteristics needed for the substrate with a multilayerreflective film better in addition to the effect of significantlysuppressing detection of false defects in the defect inspection usingthe high-sensitivity defect inspection apparatuses according to theninth to eleventh configurations.

(Thirteenth Configuration)

A thirteenth configuration of the invention is a substrate with amultilayer reflective film comprising a multilayer reflective filmhaving a high refractive index layer and a low refractive index layeralternately laminated on a main surface of a mask blank substrate foruse in lithography, wherein a surface of the substrate with a multilayerreflective film has a root mean square roughness (Rms) of not more than0.15 nm, obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, and has a power spectrum density of not more than 20 nm⁴ ata spatial frequency of not less than 1 μm⁻¹.

According to the thirteenth configuration, the surface of the substratewith a multilayer reflective film has the root mean square roughness(Rms) of not more than 0.15 nm, obtained by measuring an area of 1 μm×1μm with an atomic force microscope, and has the power spectrum densityof not more than 20 nm⁴ at a spatial frequency of not less than 1 μm⁻¹,making the reflectance characteristics need for the substrate with amultilayer reflective film better, and making it possible to suppressdetection of false defects in defect inspection of the multilayerreflective film using a high-sensitivity defect inspection apparatus,and further make the critical defects more noticeable. In addition, itis possible to significantly suppress detection of false defects in thedefect inspection using a high-sensitivity defect inspection apparatuswith inspection light in the wavelength range of 150 nm to 365 nm, e.g.,a UV laser with an inspection light source wavelength of 266 nm or anArF excimer laser with an inspection light source wavelength of 193 nm,or a high-sensitivity defect inspection apparatus with inspection light(EUV light) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm.

(Fourteenth Configuration)

A fourteenth configuration of the invention is a substrate with amultilayer reflective film according to the thirteenth configuration,wherein the substrate with a multilayer reflective film has a protectivefilm on the multilayer reflective film.

According to the fourteenth configuration, the substrate with amultilayer reflective film has the protective film on the multilayerreflective film to suppress damages to the multilayer reflective film atthe time of fabricating a transfer mask (EUV mask), so that thereflectance characteristics to EUV light become better. The substratewith a multilayer reflective film makes it possible to suppressdetection of false defects in the defect inspection of the surface ofthe protective film using a high-sensitivity defect inspectionapparatus, and further make the critical defects more noticeable. Inaddition, it is possible to significantly suppress detection of falsedefects in the defect inspection using a high-sensitivity defectinspection apparatus with inspection light in the wavelength range of150 nm to 365 nm, e.g., a UV laser with an inspection light sourcewavelength of 266 nm or an ArF excimer laser with an inspection lightsource wavelength of 193 nm, or a high-sensitivity defect inspectionapparatus with inspection light (EUV light) in the wavelength range of0.2 nm to 100 nm, e.g., a high-sensitivity defect inspection apparatuswith EUV light with an inspection light source wavelength of 13.5 nm.

(Fifteenth Configuration)

A fifteenth configuration of the invention is a substrate with amultilayer reflective film according to the thirteenth or fourteenthconfiguration, wherein the surface of the multilayer reflective film orthe protective film of the substrate with a multilayer reflective filmhas a power spectrum density of not more than 20 nm⁴, obtained bymeasuring an area of 1 μm×1 μm with an atomic force microscope, at aspatial frequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹.

According to the fifteenth configuration, it is possible tosignificantly suppress detection of false defects in the defectinspection of the substrate with a multilayer reflective film using ahigh-sensitivity defect inspection apparatus with inspection light inthe wavelength range of 150 nm to 365 nm, e.g., a UV laser with aninspection light source wavelength of 266 nm or an ArF excimer laserwith an inspection light source wavelength of 193 nm, thereby making thecritical defects more noticeable.

(Sixteenth Configuration)

A sixteenth configuration of the invention is a substrate with amultilayer reflective film according to the thirteenth or fourteenthconfiguration, wherein the surface of the multilayer reflective film orthe protective film of the substrate with a multilayer reflective filmhas a power spectrum density of not more than 9 nm⁴, obtained bymeasuring an area of 1 μm×1 μm with an atomic force microscope, at aspatial frequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹.

According to the sixteenth configuration, it is possible tosignificantly suppress detection of false defects in the defectinspection using a high-sensitivity defect inspection apparatus withinspection light (EUV light) in the wavelength range of 0.2 nm to 100nm, e.g., a high-sensitivity defect inspection apparatus with EUV lightwith an inspection light source wavelength of 13.5 nm.

(Seventeenth Configuration)

A seventeenth configuration of the invention is a transmissive maskblank comprising a light shielding function film to be a transferpattern on the main surface of the mask blank substrate according to anyone of the first to fourth configurations.

According to the seventeenth configuration, in the transmissive maskblank, the main surface of the mask blank substrate is configured insuch a way that the power spectrum density, which is the amplitudeintensity of all roughness components detectable in an area of 1 μm×1μm, at a spatial frequency of not less than 1 μm⁻¹, is set to not morethan 10 nm⁴, making it possible to suppress detection of false defectsin the defect inspection using a high-sensitivity defect inspectionapparatus, thereby making the critical defects more noticeable. Inaddition, it is possible to significantly suppress detection of falsedefects in the defect inspection using a high-sensitivity defectinspection apparatus using an ArF excimer laser with an inspection lightsource wavelength of 193 nm.

(Eighteenth Configuration)

An eighteenth configuration of the invention is a reflective mask blankcomprising an absorber film to be a transfer pattern on the multilayerreflective film or the protective film of the substrate with amultilayer reflective film according to any one of the eighth tosixteenth configurations.

According to the eighteenth configuration, it is possible to suppressdetection of false defects in the defect inspection on the reflectivemask blank using a high-sensitivity defect inspection apparatus, andfurther make the critical defects more noticeable. In addition, it ispossible to significantly suppress detection of false defects in thedefect inspection using a high-sensitivity defect inspection apparatuswith inspection light in the wavelength range of 150 nm to 365 nm, e.g.,a UV laser with an inspection light source wavelength of 266 nm or anArF excimer laser with an inspection light source wavelength of 193 nm,or a high-sensitivity defect inspection apparatus with inspection light(EUV light) in the wavelength range of 0.2 nm to 100 nm, e.g., ahigh-sensitivity defect inspection apparatus with EUV light with aninspection light source wavelength of 13.5 nm.

(Nineteenth Configuration)

A nineteenth configuration of the invention is a transmissive maskcomprising a light shielding function film pattern provided on the mainsurface by patterning the light shielding function film of thetransmissive mask blank according to the seventeenth configuration.

(Twentieth Configuration)

A twentieth configuration of the invention is a reflective maskcomprising an absorber pattern provided on the multilayer reflectivefilm by patterning the absorber film of the reflective mask blankaccording to the eighteenth configuration.

According to the nineteenth and twentieth configurations, it is possibleto suppress detection of false defects in the defect inspection on thetransmissive mask and the reflective mask using a high-sensitivitydefect inspection apparatus, making the critical defects morenoticeable.

(Twenty-First Configuration)

A twenty-first configuration of the invention is a method ofmanufacturing a semiconductor device, comprising a step of forming atransfer pattern on a transferred substrate using the transmissive maskaccording to the nineteenth configuration by performing a lithographyprocess using an exposure device.

(Twenty-Second Configuration)

A twenty-second configuration of the invention is a method ofmanufacturing a semiconductor device, comprising a step of forming atransfer pattern on a transferred substrate using the reflective maskaccording to the twentieth configuration by performing a lithographyprocess using an exposure device.

According to the twenty-first and twenty-second configurations, atransmissive mask or a reflective mask from which critical defects suchas a foreign matter or scratches is removed can be used in defectinspection using a high-sensitivity defect inspection apparatus, so thata transfer pattern such as a circuit pattern to be transferred onto aresist film formed on a transferred substrate such as a semiconductorsubstrate is free of defects. This makes it possible to manufacture asemiconductor device having a fine and high-precision transfer pattern.

Effects of the Invention

The mask blank substrate, a substrate with a multilayer reflective film,the transmissive mask blank, the reflective mask blank, the transmissivemask and the reflective mask according to the invention permit detectionof false defects originating from the surface roughness of a substrateand a film to be suppressed in defect inspection using ahigh-sensitivity defect inspection apparatus, and facilitate thedetection of critical defects such as foreign matters and scratches. Inthe mask blank substrate, the substrate with a multilayer reflectivefilm, the reflective mask blank and the reflective mask for use in EUVlithography, in particular, the multilayer reflective film formed on themain surface of the substrate provides high reflectance whilesuppressing false defects.

According to the above-described method of manufacturing a semiconductordevice, a reflective mask or a transmissive mask from which criticaldefects such as a foreign matter or scratches is removed can be used indefect inspection using a high-sensitivity defect inspection apparatus,so that a transfer pattern such as a circuit pattern to be formed on atransferred substrate such as a semiconductor substrate is free ofdefects. This makes it possible to manufacture a semiconductor devicehaving a fine and high-precision transfer pattern.

Description of Illustrated Embodiments

[Mask Blank Substrate]

A mask blank substrate according to an exemplary embodiment of thepresent invention is described as follows.

FIG. 1(a) is a perspective view illustrating a mask blank substrate 10according to an exemplary embodiment of the present invention. FIG. 1(b)is a schematic cross-sectional view illustrating the mask blanksubstrate 10 of the present embodiment.

A mask blank substrate 10 (or simply referred to as substrate 10) is arectangular plate-like body, and includes two opposite main surfaces 2and end faces 1. The two opposite main surfaces 2 are an upper surfaceand a lower surface of the plate-like body, and are formed so as to faceeach other. At least one of the two opposite main surfaces 2 is the mainsurface where a transfer pattern is formed.

The end faces 1 are side surfaces of the plate-like body, and areadjacent to the outer edges of the opposite main surfaces 2. The endface 1 has a flat end face portion 1 d and a curved end face portion 1f. The flat end face portion 1 d is a surface connecting the side of oneopposite main surface 2 and the side of the other opposite main surface2, and includes a side surface portion 1 a and a chamfered inclinedsurface portion 1 b. The side surface portion 1 a is that portion (Tside) in the flat end face portion 1 d which is substantiallyperpendicular to the opposing main surfaces 2. The chamfered inclinedsurface portion 1 b is a chamfered portion (C side) between the sidesurface portion 1 a and the opposite main surface 2, and is formedbetween the side surface portion 1 a and the opposite main surface 2.

The curved end portions 1 f is a portion (R portion) adjacent to thevicinity of a corner portion 10 a of the substrate 10 in a plan view ofthe substrate 10, and includes a side surface portion 1 c and achamfered inclined portion 1 e. The plan view of the substrate 10 is,for example, is to see the substrate 10 from a direction perpendicularto the opposite main surface 2. Further, the corner portion 10 a of thesubstrate 10 is, for example, the vicinity of the intersection of thetwo sides at the outer edge of the opposite main surface 2. Theintersection of the two sides may be the intersection of the extensionsof the two sides. In this embodiment, the curved end portion 1 f isformed into a curved shape by rounding the corner portion 10 a of thesubstrate 10.

To achieve the above objects, this embodiment is characterized in thatat least the main surface on which a transfer pattern is formed, thatis, the main surface on that side of a transmissive mask blank 50 wherea light shielding function film 51 is formed, or the main surface onthat side of a reflective mask blank 30 where a multilayer reflectivefilm 21, a protective film 22, and an absorber film 24 are formed, asdescribed later, has a certain surface roughness and a certain powerspectrum density (PSD).

The surface roughnesses (Rmax, Rms) and power spectrum density (PSD),which are parameters representing the surface states of the mainsurfaces of the mask blank substrate 10 of this embodiment, aredescribed as follows.

First, Rms (Root Means Square), which is a representative index of thesurface roughness, is the root mean square roughness that is the squareroot of the mean value of the square of the deviation from an averageline to a measurement curve. Rms is expressed by the following equation(1).

$\begin{matrix}\left\lbrack {{Eq}.\mspace{14mu} 1} \right\rbrack & \; \\{{Rms} = \sqrt{\frac{1}{l}{\int_{0}^{l}{{Z^{2}(x)}d\; x}}}} & (1)\end{matrix}$

In the equation (1), 1 is a reference length, and Z is the height fromthe average line to the measurement curve.

Rmax, which is likewise a representative index of the surface roughness,is the height of the maximum surface roughness, Rmax is the maximumheight of the surface roughness or the difference between the absolutevalue of the maximum value of the height of the crest of the roughnesscurve and the absolute value of the maximum value of the depth of thetrough of the roughness curve.

Rms and Rmax have been used to manage the surface roughness of the maskblank substrate 10, and are excellent in that the surface roughness canbe grasped by a numeral. However, Rms and Rmax are both heightinformation and do not include information about a change in a finesurface shape.

By contrast, power spectrum analysis, which converts an obtainedroughness of the surface to the spatial frequency region to representthe surface roughness by the amplitude intensity in terms of the spatialfrequency, can quantify a fine surface shape. It is provided that Z (x,y) is data on the heights of the x coordinate and the y coordinate,Fourier transform of Z (x, y) is given by the following equation (2).

$\begin{matrix}\left\lbrack {{Eq}.\mspace{14mu} 2} \right\rbrack & \; \\{{F\left( {u,v} \right)} = {\frac{1}{N_{x}N_{y}}{\sum\limits_{u = 0}^{N_{x} - 1}{\sum\limits_{v = 0}^{N_{y} - 1}{{Z\left( {x,y} \right)}{\exp\left\lbrack {{- i}\; 2{\pi\left( {\frac{ux}{N_{x}} + \frac{vy}{N_{y}}} \right)}} \right\rbrack}}}}}} & (2)\end{matrix}$

where Nx and Ny are the numbers of data in the x and y directions. Atu=0, 1, 2··Nx−1, and v=0, 1, 2·Ny−1, the spatial frequency f is given bythe following equation (3).

$\begin{matrix}\left\lbrack {{Eq}.\mspace{14mu} 3} \right\rbrack & \; \\{f = \left\{ {\left\lbrack \frac{u}{\left( {N_{x} - 1} \right)d_{x}} \right\rbrack^{2} + \left\lbrack \frac{v}{\left( {N_{y} - 1} \right)d_{y}} \right\rbrack^{2}} \right\}^{1/2}} & (3)\end{matrix}$

In the equation (3), dx is the minimum resolution of the x direction,and dy is the minimum resolution in the y direction.

The power spectrum density PSD in this case is given by the followingequation (4).[Eq. 4]P(u,v)=|F(u,v)|²  (4)

The power spectral analysis is excellent in that the main surfaces 2 ofthe substrate 10 and a change in the surface state of a film, which willbe described later, can be grasped not only as a simple change in heightbut also a change in spatial frequency. The power spectral analysis is amethod to analyze the influence of microscopic reactions at the atomiclevel on the surface.

To achieve the aforementioned objects, the mask blank substrate 10according to this embodiment is configured so that the main surface onwhich a transfer pattern is formed is expressed in terms of theaforementioned surface roughness (Rms) and power spectrum density, andhas a root mean square roughness (Rms) of not more than 0.15 nm obtainedby measuring an area of 1 μm×1 μm with an atomic force microscope, andhas a power spectrum density of not more than 10 nm⁴ at a spatialfrequency of not less than 1 μm⁻¹.

According to the present invention, the area of 1 μm×1 μm may be anarbitrary location of the area where the transfer pattern is formed.When the substrate 10 has a size of 6025 (152.4 mm×152.4 mm×6.35 mm),for example, the area may be an area of 142 mm×142 mm, an area of 132mm×132 mm, or an area of 132 mm×104 mm, excluding the peripheral area ofthe main surface of the substrate 10. Further, the arbitrary locationmay be, for example, a central area of the main surface of the substrate10.

The above-described area of 1 μm×1 μm, transfer-pattern forming area,and arbitrary location may be applied to the multilayer reflective film21 and the protective film 22 of a substrate with a multilayerreflective film 20, an absorber film 24 of a reflective mask blank 30,and a light shielding function film 51 in a transmissive mask blank 50,which will be described later.

When defect inspection of the main surface of the mask blank substrate10 is performed using a high-sensitivity defect inspection apparatuswith inspection light in the wavelength range of 150 nm to 365 nm, e.g.,a UV laser with an inspection light source wavelength of 266 nm or anArF excimer laser with an inspection light source wavelength of 193 nm,it is desirable that the main surface should preferably have a powerspectrum density of not more than 10 nm⁴, obtained by measuring an areaof 1 μm×1 μm with an atomic force microscope, at a spatial frequency ofnot less than 1 μm⁻¹ and not more than 10 μm⁻¹, more preferably, a powerspectrum density of not less than 1 nm⁴ and not more than 10 nm⁴ at aspatial frequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹,more preferably, a power spectrum density of not less than 1 nm⁴ and notmore than 8 nm⁴ at a spatial frequency of not less than 1 μm⁻¹ and notmore than 10 μm⁻¹, and more preferably, a power spectrum density of notless than 1 nm⁴ and not more than 6 nm⁴ at a spatial frequency of notless than 1 μm⁻¹ and not more than 10 μm⁻¹.

Further, it is desirable that the aforementioned root mean squareroughness (Rms) should preferably be not more than 0.12 nm, morepreferably, not more than 0.10 nm, more preferably, not more than 0.08nm, and more preferably, not more than 0.06 nm. In addition, it isdesirable that the maximum height (Rmax) should preferably be not morethan 1.2 nm, more preferably, not more than 1.0 nm, more preferably, notmore than 0.8 nm, and more preferably, not more than 0.6 nm. From theviewpoint of improvements on the optical properties such as thereflectivities of the multilayer reflective film 21, the protective film22, the absorber film 24 and the light shielding function film 51 formedon the mask blank substrate 10, it is preferable to manage bothparameters, the root mean square roughness (Rms) and the maximum height(Rmax). For example, it is desirable that the preferable surfaceroughness of the mask blank substrate 10 should preferably be such thatthe root mean square roughness (Rms) is preferably not more than 0.12 nmand the maximum height (Rmax) is not more than 1.2 nm, more preferably,the root mean square roughness (Rms) is not more than 0.10 nm and themaximum height (Rmax) is not more than 1.0 nm, more preferably, the rootmean square roughness (Rms) is not more than 0.08 nm and the maximumheight (Rmax) is not more than 0.8 nm, and more preferably, the rootmean square roughness (Rms) is not more than 0.06 nm and the maximumheight (Rmax) is not more than 0.6 nm.

Further, it is preferable that the main surface of the substrate 10should be a surface treated by catalyst-referred etching.CAtalyst-Referred Etching (hereinafter also referred to as CARE) is asurface treatment method selectively removing fine convex portionspresent on the main surface to smooth the main surface by active speciesgenerated from the molecules of the treatment liquid which are adsorbedto the catalyst, by making the main surface of the substrate 10 and thecatalyst to move closer or come in contact with each other while atreatment fluid that do not exhibit solubility in a normal state isinterposed between the main surface of the substrate 10 and thecatalyst.

According to the fourth configuration, because the main surface of thesubstrate 10 is selectively subjected to a surface treatment from convexportions contacting the surface of the catalyst which is a referencesurface by catalyst-referred etching, irregularities (surface roughness)forming the main surface become highly aligned surface states whilebeing kept very smooth, and become such surface states that the ratio ofconcave portions is greater than the ratio of convex portions withrespect to the reference surface. When a plurality of thin films arelaminated on the main surface, the size of defects on the main surfacetend to become smaller, which is preferable from the viewpoint of thedefect quality. Particularly, the effect is demonstrated when amultilayer reflective film to be described later is formed on the mainsurface. Further, execution of a surface treatment to the main surfaceby catalyst-referred etching as mentioned above makes it possible torelatively easily form the surface with the surface roughness and thebearing curve characteristics as defined in the first or secondconfiguration.

When the material for the substrate 10 is a glass material, at least onematerial selected from the group of platinum, gold, a transition metal,and an alloy comprising at least one thereof may be available as thecatalyst. Further, at least one solution selected from the group offunctional water such as pure water, ozone water or hydrogen water, alow-concentration alkaline aqueous solution, and a low-concentrationacidic aqueous solution may be available as the treatment solution.

With the surface roughness of the main surface and the power spectrumdensity being set in the above-described ranges, as described above, itis possible to significantly suppress detection of false defects indefect inspection with, for example, the mask substrate/blank defectinspection apparatus “MAGICS M7360” for EUV exposure of Lasertec Corp.(inspection light source wavelength: 266 nm), the reticle, the opticalmask/blank and the EUV mask/blank defect inspection apparatus “Teron 600series” of KLA-Tencor Corp. (inspection light source wavelength: 193nm).

It is noted that the inspection light source wavelength is not limitedto 266 nm and 193 nm. 532 nm, 488 nm, 364 nm, and 257 nm may be used asthe inspection light source wavelength.

The mask blank substrates to be subjected to defect inspection using ahigh-sensitivity defect inspection apparatus with the inspection lightsource wavelength described above include a transmissive mask blanksubstrate, and a reflective mask blank substrate.

When defect inspection of the main surface of the mask blank substrate10 is performed using a high-sensitivity defect inspection apparatuswith inspection light (EUV light) in the wavelength range of 0.2 nm to100 nm, e.g., a high-sensitivity defect inspection apparatus with UVlight with an inspection light source wavelength of 13.5 nm, it isdesirable that the main surface should more preferably have a powerspectrum density of not more than 5 nm⁴, obtained by measuring an areaof 1 μm×1 μm with an atomic force microscope, at a spatial frequency ofnot less than 10 μm⁻¹ and not more than 100 μm⁻¹, more preferably, apower spectrum density of not less than 0.5 nm⁴ and not more than 5 nm⁴at a spatial frequency of not less than 10 μm⁻¹ and not more than 100μm⁻¹. It is noted that when defect inspection of the main surface of themask blank substrate 10 is performed using a high-sensitivity defectinspection apparatus with EUV light, a predetermined reflectance orhigher is needed so that the material is limited to one other thanglass.

With the surface roughness of the main surface and the power spectrumdensity being set in the above-described ranges, as described above, itis possible to significantly suppress detection of false defects indefect inspection using, for example, a high-sensitivity defectinspection apparatus with EUV light with an inspection light sourcewavelength of 13.5 nm.

The mask blank substrate 10 to be subjected to defect inspection using ahigh-sensitivity defect inspection apparatus with the aforementionedinspection light wavelength includes a reflective mask blank substrate.

It is preferable that the main surface of the mask blank substrate 10according to this embodiment on which a transfer pattern is formedshould be treated to have a high flatness at least from the viewpoint ofobtaining the pattern transfer accuracy and position precision. For anEUV reflective mask blank substrate, it is preferable that the flatnessof an area of 132 mm×132 mm or an area of 142 mm×142 mm of the mainsurface of the substrate 10 on which a transfer pattern is formed shouldbe not more than 0.1 μm, particularly preferably, not more than 0.05 μm.It is more preferable that the flatness of an area of 132 mm×132 mm ofthe main surface where a transfer pattern is formed should be not morethan 0.03 μm. Further, the main surface opposite to the main surface ofthe substrate 10 on which a transfer pattern is formed is a surface thatis electrostatically chucked when the substrate 10 is set in theexposure apparatus, the flatness of an area of 142 mm×142 mm is not morethan 1 μm, particularly preferably, not more than 0.5 μm. For the maskblank substrate 10 to be used for a transmissive mask blank for exposureby an ArF excimer laser, the flatness of an area of 132 mm×132 mm or anarea of 142 mm×142 mm of the main surface of the substrate 10 on which atransfer pattern is formed should be not more than 0.3 μm, particularlypreferably, not more than 0.2 μm.

Any material transparent to the exposure wavelength is available as amaterial for a transmissive mask blank substrate for exposure by an ArFexcimer laser. In general, synthetic quartz glass is used. Otheravailable materials may be aluminosilicate glass, soda-lime glass,borosilicate glass, and non-alkali glass.

Any material having a low thermal expansion property is available as amaterial for a reflective mask blank substrate for EUV exposure. Forexample, a SiO₂—TiO₂ glass (2-element based (SiO₂—TiO₂) and 3-elementbased (SiO₂—TiO₂—SnO₂ or the like)), e.g., what is called multi-elementglass such as SiO₂—Al₂O₂—Li₂O based crystallized glass, is available. Inaddition, a substrate of silicon or metal in addition to a glasssubstrate may be used. Examples of the metal substrate include an Invaralloy (Fe—Ni-based alloy).

As described above, because the mask blank substrate for EUV exposureneeds low thermal expansion characteristics, is required in thesubstrate, a multi-element glass material is used; however, thismaterial undesirably has a difficulty in obtaining high smoothness ascompared with synthetic silica glass. To solve this problem, a thin filmmade of a metal, an alloy or a material containing at least one ofoxygen, nitrogen, carbon contained in either the metal or the alloy isformed on a substrate made of a multi-element glass material. Then, thesurface of such a thin film is subjected to mirror polishing and asurface treatment, making it possible to relatively easily form asurface with the surface roughness and the power spectrum density in theaforementioned range.

As the material for the thin film, for example, Ta (tantalum), an alloycontaining Ta or a Ta compound containing at least one of oxygen,nitrogen, carbon contained in either the metal or the alloy ispreferable. As the Ta compound, for example, TaB, TaN, TaO, TaON, TaCON,TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi,TaSiO, TaSiN, TaSiON, TaSiCON and the like may be used. Of these Tacompounds, TaN, TaON, TaCON, TaBN, TaBON, TaBCON, TaHfN, TaHfON,TaHfCON, TaSiN, TaSiON, and TaSiCON containing nitrogen (N) are morepreferable. It is desirable that in view of the high smoothness of thesurface of the thin film, the thin film should have an amorphousstructure. The crystal structure of the thin film can be measured byX-ray diffractometer (XRD).

The processing method for obtaining the surface roughness and powerspectrum density as specified above is not particularly limited in theinvention. The invention is characterized in that the surface roughnessand the power spectrum density of the mask blank substrate are managed,which may be achieved by, for example, processing methods illustrated inExamples 1 to 3 and 5 to be described later.

[Substrate with a Multilayer Reflective Film]

The substrate with a multilayer reflective film 20 according to anexemplary embodiment of the invention is described as follows.

FIG. 2 is a schematic diagram illustrating a substrate with a multilayerreflective film 20 according to this embodiment.

The substrate with a multilayer reflective film 20 according to theembodiment has a structure in which the multilayer reflective film 21 isprovided on the main surface of the above-described mask blank substrate10 where a transfer pattern is formed. This multilayer reflective film21 provides a reflective mask for EUV lithography with the capability ofreflecting EUV light, and has a structure of a multilayer reflectivefilm having elements of different reflectances laminated periodically.

The material for the multilayer reflective film 21 is not particularlylimited as long as it reflects EUV light; the reflective multilayer film21 generally has a reflectance of not less than 65% by itself, and hasan upper reflectance limit of 73%. In general, such a multilayerreflective film 21 may have thin films made of a material with a highrefractive index (high refractive index layers) and thin films made of amaterial with a low refractive index (low refractive index layers)alternately laminated by about 40 to 60 periods.

For example, it is preferable that the multilayer reflective film 21 forEUV light with a wavelength of 13 nm to 14 nm is an Mo/Si periodicmultilayer film having Si films and Mo films alternately laminated byabout 40 periods. As other multilayer reflective films for use in theregion of EUV light, an Ru/Si periodic multilayer film, an Mo/Beperiodic multilayer film, an Mo compound/Si compound periodic multilayerfilm, a Si/Nb periodic multilayer film, a Si/Mo/Ru periodic multilayerfilm, a Si/Mo/Ru/Mo periodic multilayer film, and a Si/Ru/Mo/Ru periodicmultilayer film are available.

The methods of forming the multilayer reflective film 21 are known inthe art; for example, the multilayer reflective film 21 may be formed bydepositing individual layers by magnetron sputtering, ion beamsputtering or the like. For the aforementioned Mo/Si periodic multilayerfilm, for example, the multilayer reflective film 21 is formed by ionbeam sputtering to deposit a film with a thickness of about severalnanometers on the substrate 10 using a Si target first, then deposit aMo film with a thickness of about several nanometers using an Mo target,as one period, and then laminate those two films by 40 to 60 periods.

To protect the multilayer reflective film 21 from dry etching or wetcleaning in the process of manufacturing a reflective mask for EUVlithography, the protective film 22 (see FIG. 3) may be formed on themultilayer reflective film 1 formed as described above. The structurewith the multilayer reflective film 21 and the protective film 22 on themask blank substrate 10 may be included in the substrate with amultilayer reflective film according to invention.

As the material for the protective film 22, for example, materials suchas Ru, Ru—(Nb, Zr, Y, B, Ti, La, Mo), Si—(Ru, Rh, Cr, B), Si, Zr, Nb, Laand B can be used. Of the materials, if those containing ruthenium (Ru)applied, reflectance characteristics of the multilayer reflective filmbecome better. Specifically, Ru and Ru—(Nb, Zr, Y, B, Ti, La, Mo) arepreferred. Such a protective film is particularly effective when theabsorber film is formed of a Ta-based material and is patterned by dryetching with Cl-based gas.

It is preferable that the surface of the multilayer reflective film 21or the protective film 22 of the substrate with a multilayer reflectivefilm 20 should have a power spectrum density of not more than 20 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm and not morethan 10 μm⁻¹. This configuration makes it possible to suppress detectionof false defects in the defect inspection of the surface of themultilayer reflective film 21 or the protective film 22 using ahigh-sensitivity defect inspection apparatus, thereby making thecritical defects more noticeable. It is desirable that the surface ofthe multilayer reflective film 21 or the protective film 22 should morepreferably have a power spectrum density of not more than 17 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹, more preferably, a power spectrum density of not more than15 nm⁴, obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹, more preferably, a power spectrum density of not more than10 nm⁴, obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹, and more preferably, a power spectrum density of not lessthan 1 nm⁴ and not more than 10 nm⁴, obtained by measuring an area of 1μm×1 μm with an atomic force microscope, at a spatial frequency of notless than 1 μm⁻¹ and not more than 10 μm⁻¹. This configuration makes itpossible to significantly suppress detection of false defects whendefect inspection of the substrate with a multilayer reflective film 20is performed using a high-sensitivity defect inspection apparatus withinspection light in the wavelength range of 150 nm to 365 nm, e.g., ahigh-sensitivity defect inspection apparatus using a UV laser with aninspection light source wavelength of 266 nm or an ArF excimer laserwith an inspection light source wavelength of 193 nm.

It is preferable that the surface of the multilayer reflective film 21or the protective film 22 of the substrate with a multilayer reflectivefilm 20 should have a power spectrum density of not more than 9 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 10 μm⁻¹ and not morethan 100 μm⁻¹. It is desirable that the surface of the multilayerreflective film 21 or the protective film 22 should more preferably havea power spectrum density of not more than 8 nm⁴, obtained by measuringan area of 1 μm×1 μm with an atomic force microscope, at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹, morepreferably, a power spectrum density of not more than 7 nm⁴, obtained bymeasuring an area of 1 μm×1 μm with an atomic force microscope, at aspatial frequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹,more preferably, a power spectrum density of not more than 5 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 10 μm⁻¹ and not morethan 100 μm⁻¹, and more preferably, a power spectrum density of not lessthan 0.5 nm⁴ and not more than 5 nm⁴, obtained by measuring an area of 1μm×1 μm with an atomic force microscope, at a spatial frequency of notless than 10 μm⁻¹ and not more than 100 μm⁻¹. This configuration makesit possible to significantly suppress detection of false defects whendefect inspection of the substrate with a multilayer reflective film isperformed using a high-sensitivity defect inspection apparatus withinspection light (EUV light) in the wavelength range of 0.2 nm to 100nm, e.g., a high-sensitivity defect inspection apparatus using EUV lightwith an inspection light source wavelength of 13.5 nm.

To make the reflectance characteristics needed for the substrate with amultilayer reflective film in addition to the effect of significantlysuppressing detection of false defects in defect inspection using theaforementioned high-sensitivity defect inspection apparatus, it ispreferable that the surface of the multilayer reflective film 21 or theprotective layer 22 should have a root mean square roughness (Rms) ofnot more than 0.15 nm, obtained by measuring an area of 1 μm×1 μm withan atomic force microscope. It is desirable that the root mean squareroughness (Rms) should more preferably be not more than 0.13 nm, and theroot mean square roughness (Rms) should more preferably be not more than0.12 nm.

To permit the surface of the multilayer reflective film 21 or theprotective film 22 to have a power spectrum density in theaforementioned range while maintaining the surface state of thesubstrate 10 in the aforementioned range, the multilayer reflective film21 is deposited by obliquely depositing a high refractive index layerand a low refractive index layer with respect to the normal line of themain surface of the substrate 10. More specifically, deposition isperformed by ion beam sputtering in such a way that the incident angleof sputtered particles for deposition of high refractive index layersconstituting the multilayer reflective film 21 becomes greater than theincident angle of sputtered particles for deposition of low refractiveindex layers with respect to the normal line of the main surface of thesubstrate 10. In further details, the incident angle of sputteredparticles for deposition of low refractive index layers of Mo or thelike should be not less than 40 degrees and less than 90 degrees, andthe incident angle of sputtered particles for the deposition of highrefractive index layer of Si or the like should be not less than 0degrees and not more than 60 degrees. Furthermore, the protective film22 that is formed on the multilayer reflective film 21 is consecutivelyformed after deposition of the multilayer reflective film 21 in such away that the protective film 22 is deposited obliquely with respect tothe normal line of the main surface of the substrate 10.

Further, for the substrate 10 whose surface state does not lie withinthe aforementioned range, or to suppress detection of false defects inhigh-sensitivity defect inspection of the multilayer reflective film 21or the protective film 22, the multilayer reflective film 21 should bedeposited with the incident angle of sputtered particles for depositionof a low refractive index layer of Mo or the like and the incident angleof sputtered particles for deposition of a high refractive index layerof Si or the like being set to small angles, e.g., not less than 0degrees and not more than 30 degrees.

A back-side conductive film 23 (see FIG. 3) may be formed on that sideof the substrate with a multilayer reflective film 20 which is oppositeto the side contacting the multilayer reflective film 21 of thesubstrate 10 for the purpose of electrostatic chuck. The structure withthe multilayer reflective film 21 and the protective film 22 on thatside of the mask blank substrate 10 where a transfer pattern is formed,and the back-side conductive film 23 is provided on that side which isopposite to the side contacting the multilayer reflective film 21 may beincluded in the substrate with a multilayer reflective film according toinvention. The electrical property (sheet resistance) required for theback-surface conductive film 23 is typically not more than 100Ω/□. Themethod of forming the back-side conductive film 23 is known; forexample, the back-side conductive film 23 may be formed by magnetronsputtering or ion beam sputtering method by using a target of metal oran alloy of Cr, Ta or the like.

As the substrate with a multilayer reflective film 20 according to theembodiment, a base layer (an under layer) may be formed between thesubstrate 10 and the multilayer reflective film 21. The base layer maybe formed for the purposes of improving smoothness of the main surfaceof the substrate 10, reducing defects, increasing the reflectance of themultilayer reflective film 21, and correcting the stress on themultilayer reflective film 21.

[Reflective Mask Blank]

Next, the reflective mask blank 30 according to an exemplary embodimentof the present invention is described below.

FIG. 3 is a schematic diagram illustrating the reflective mask blank 30according to this embodiment.

The reflective mask blank 30 according to the embodiment is configuredto have the absorber film 24, to be a transfer pattern, formed on theprotective layer 22 of the above-described substrate with a multilayerreflective film 20.

The material for the absorber film 24 is not particularly limited. Forexample, it is preferable to use Ta (tantalum) alone or those containingTa as the main component among materials capable of absorbing EUV light.Usually, the material containing Ta as the main component is a Ta alloy.The crystalline state of such an absorber film should preferably have anamorphous or microcrystalline structure from the viewpoint of thesmoothness and the flatness. As the material containing Ta as the maincomponent, for example, a material containing Ta and B, a materialcontaining Ta and N, a material containing Ta and B and furthercontaining at least one of O and N, a material containing Ta and Si, amaterial containing Ta, Si and N, a material containing Ta and Ge, and amaterial containing Ta, Ge and N may be used. In addition, adding B, Si,Ge or the like to Ta easily provides an amorphous structure, whichimproves the smoothness. Further, adding N or O to Ta improvesresistance against oxidation, making it possible to improve thestability over time. To permit the surface of the absorber film 24 tohave a power spectrum density in the aforementioned range whilemaintaining the surface states of the substrate 10 and the substratewith a multilayer reflective film 20 in the aforementioned ranges, theabsorber film 24 should preferably have an amorphous structure. Thecrystal structure can be observed with an X-ray diffractometer (XRD).

It is desirable that the surface of the absorber film 24 shouldpreferably have a power spectrum density of not more than 10 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm and not morethan 10 μm⁻¹, more preferably, a power spectrum density of not less than1 nm⁴ and not more than 10 nm⁴, obtained by measuring an area of 1 μm×1μm with an atomic force microscope, at a spatial frequency of not lessthan 1 μm⁻¹ and not more than 10 μm⁻¹. This configuration makes itpossible to significantly suppress detection of false defects whendefect inspection of the reflective mask blank 30 is performed using ahigh-sensitivity defect inspection apparatus with inspection light inthe wavelength range of 150 nm to 365 nm, e.g., a high-sensitivitydefect inspection apparatus using a UV laser with an inspection lightsource wavelength of 266 nm or an ArF excimer laser with an inspectionlight source wavelength of 193 nm.

It is preferable that the surface of the absorber film 24 shouldpreferably have more preferably, a power spectrum density of not morethan 5 nm⁴, obtained by measuring an area of 1 μm×1 μm with an atomicforce microscope, at a spatial frequency of not less than 10 μm⁻¹ andnot more than 100 μm⁻¹, and more preferably, a power spectrum density ofnot less than 0.5 nm⁴ and not more than 5 nm⁴, obtained by measuring anarea of 1 μm×1 μm with an atomic force microscope, at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹. Thisconfiguration makes it possible to significantly suppress detection offalse defects when defect inspection of the reflective mask blank 30 isperformed using a high-sensitivity defect inspection apparatus withinspection light (EUV light) in the wavelength range of 0.2 nm to 100nm, e.g., a high-sensitivity defect inspection apparatus using EUV lightwith an inspection light source wavelength of 13.5 nm.

The reflective mask blank according to the invention is not limited tothe configuration illustrated in FIG. 3. For example, a resist film tobe a mask for patterning the absorber film 24 may be formed on theabsorber film, so that the reflective mask blank with resist-film 30 maybe regarded as the reflective mask blank according to the invention. Theresist film to be formed on the absorber film 24 may be a positive typeor a negative type. Further, the reflective mask blank may be used forlaser drawing as well as for electron beam writing. Furthermore, what iscalled a hard mask film (an etching mask film) may be formed between theabsorber film 24 and the resist film, and this structure may also beincluded in the reflective mask blank according to invention.

[Reflective Mask]

Next, a reflective mask 40 according to an exemplary embodiment of thepresent invention is described below.

FIG. 4 is a schematic diagram illustrating the reflection type mask 40of this embodiment.

The reflective mask 40 according to this embodiment is configured tohave an absorber pattern 27 formed on the protective film 22 bypatterning the absorber film 24 in the reflective mask blank 30. Whenthe reflective mask 40 according to the embodiment is exposed withexposure light such as EUV light, the exposure light is absorbed at aportion of the mask surface where the absorber film 24 is present, andthe exposure light is reflected by the protective film 22 and themultilayer reflective film 21 at the other portion where the absorberfilm 24 is removed. Accordingly, the reflective mask 40 can be used asthe reflective mask 40 for lithography.

[Transmissive Mask Blank]

A transmissive mask blank 50 according to an exemplary embodiment of thepresent invention is described as follows.

FIG. 5 is a schematic diagram illustrating the transmissive mask blank50 according to this embodiment.

The transmissive mask blank 50 according to the embodiment configured tohave a light shielding function film 51, to be a transfer pattern,formed on the main surface on that side of the above-described maskblank substrate 10 where a transfer pattern is formed.

Examples of the transmissive mask blank 50 include a binary mask blank,and a phase shift mask blank. Examples of the light shielding functionfilm 51 include what is called a halftone film that attenuates exposurelight and shifts the phase in addition to the light shielding filmcapable of blocking the exposure light.

The binary mask blank is obtained by depositing a light shielding filmfor shielding the exposure light on the mask blank substrate 10. Thislight shielding film is patterned to form a desired transfer pattern.Examples of the light shielding film include a Cr film, a Cr alloy filmcontaining optionally oxygen, nitrogen, carbon or fluorine in Cr, a filmhaving lamination thereof, a MoSi film, and a MoSi alloy film optionallycontaining oxygen, nitrogen or carbon in MoSi, and a film havinglamination thereof. An antireflection layer having an antireflectionfunction may be included in the surface of the light shielding film.

The phase-shift mask blank is obtained by depositing a phase shift filmfor changing the phase difference of the exposure light on the maskblank substrate 10. This phase shift film is patterned to form a desiredtransfer pattern. Examples of the phase shift film include, in additionto a SiO₂ film having only a phase shift capability, a halftone filmhaving a light shielding capability and a phase shift capability, suchas a metal silicide oxide film, a metal silicide nitride film, a metalsilicide oxynitride film, a metal silicide oxide carbide film, a metalsilicide oxynitride carbide film (metal: transition metal such as Mo,Ti, W or Ta), a CrO film, a CrF film or a SiON film. The structure withthe light shielding film formed on the phase shift film may be includedin the phase-shift mask blank.

The transmissive mask blank 50 according to the invention is not limitedto the configuration illustrated in FIG. 5. For example, a resist film,to be a mask for patterning the light shielding function film 51, may beformed on the light shielding function film 51, so that the transmissivemask blank with the resist film may be regarded as the transmissive maskblank according to the invention. As in the above-described case, theresist film formed on the light shielding function film 51 may be of apositive type or a negative type. Further, the transmissive mask blankmay be used for laser drawing as well as for electron beam writing.Furthermore, what is called a hard mask film (an etching mask film) maybe formed between the light shielding function film 51 and the resistfilm, and this structure may also be included in the transmissive maskblank according to invention.

It is desirable that the surface of the light shielding function film 51in the aforementioned transmissive mask blank 50 should preferably havea power spectrum density of not more than 10 nm⁴, obtained by measuringan area of 1 μm×1 μm with an atomic force microscope, at a spatialfrequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹, morepreferably, a power spectrum density of not less than 1 nm⁴ and not morethan 10 nm⁴, obtained by measuring an area of 1 μm×1 μm with an atomicforce microscope, at a spatial frequency of not less than 1 μm⁻¹ and notmore than 10 μm⁻¹. This configuration makes it possible to significantlysuppress detection of false defects when defect inspection of thetransmissive mask blank 50 is performed using a high-sensitivity defectinspection apparatus with inspection light in the wavelength range of150 nm to 365 nm, e.g., a high-sensitivity defect inspection apparatususing an ArF excimer laser with an inspection light source wavelength of193 nm.

To permit the surface of the light shielding function film 51 to have apower spectrum density in the aforementioned range while maintaining thesurface state of the substrate 10 in the aforementioned range, it ispreferable that the surface of the light shielding function film 51should have an amorphous structure. The crystal structure can beobserved with an X-ray diffractometer (XRD).

[Transmissive Mask]

A transmissive mask 60 according to an exemplary embodiment of thepresent invention is described as follows.

FIG. 6 is a schematic diagram illustrating the transmissive mask 60according to the present embodiment.

The transmissive mask 60 according to this embodiment is configured tohave a light-shielding-function film pattern 61 formed on the mask blanksubstrate 10 by patterning the light shielding function film 51 in thetransmissive mask blank 50. When the transmissive mask 60 according tothe embodiment is a binary mask and is exposed with exposure light suchas ArF excimer laser light, the exposure light is shielded at a portionof the mask surface where the light shielding function film 51 ispresent, and the exposure light passes through the mask blank substrate10 at the other portion where the light shielding function film 51 isremoved. Accordingly, the transmissive mask can be used as thetransmissive mask 60 for lithography. When a halftone phase shift maskwhich is one type of phase shift mask is exposed with exposure lightsuch as ArF excimer laser light, the exposure light passes through theexposed mask blank substrate 10 at a portion of the mask surface wherethe light shielding function film 51 is removed, and the exposure lightis attenuated and passes while having a predetermined amount of phaseshift at a certain portion of the light shielding function film 51.Accordingly, the transmissive mask can be used as the transmissive mask60 for lithography. Further, the phase shift mask is not limited to theaforementioned halftone phase shift mask, and may be phase shift masksusing various phase-shifting effects, such as a Levenson type phaseshift mask.

[Method of Manufacturing Semiconductor Device]

A semiconductor device having various patterns or the like formed on asemiconductor substrate can be manufactured by transferring a transferpattern that is a circuit pattern or the like based on an absorberpattern 27 of the reflective mask 40 or the light-shielding-functionfilm pattern 61 of the transmissive mask 60, to the resist film formedon the a transfer target such as the semiconductor substrate, by alithography process using the above-described reflective mask 40 and thetransmissive mask 60, and the exposure apparatus, and through variousother processes.

It is noted that fiducial marks may be formed on the above-describedmask blank substrate 10, substrate with a multilayer reflective film 20,reflective mask blank 30 and transmissive mask blank 50, and thefiducial marks and the locations of critical defects detected with theaforementioned high-sensitivity defect inspection apparatus can bemanaged based on the coordinates. At the time of fabricating thereflective mask 40 or the transmissive mask blank 50 based on theobtained positional information (defect data), drawing data is correctedbased on the defect data and data on the transfer pattern to betransferred (circuit pattern) in such a way that the absorber pattern 27or the light-shielding-function film pattern 61 is formed at locationswhere critical defects are present, thereby reducing defects.

EXAMPLES

Examples 1 to 3 and 5 to 7 including the embodiments of the mask blanksubstrate, substrate with a multilayer reflective film, reflective maskblank and reflective mask for EUV exposure according to the invention,Comparative Examples 1 and 2 for those Examples, and Example 4 includingthe embodiments of the mask blank substrate, transmissive mask blank andtransmissive mask for ArF excimer laser exposure according to theinvention, are described as follows.

Example 1

First, Example 1 for the mask blank substrate and the substrate with amultilayer reflective film for EUV exposure, the reflective mask blankand the reflective mask for EUV exposure according to the invention, isdescribed.

<Fabrication of Mask Blank Substrate>

For a mask blank substrate 10, a SiO₂—TiO₂ glass substrate with a sizeof 152.4 mm×152.4 mm and a thickness of 6.35 mm was prepared, and thetop and bottom sides of the glass substrate were polished step by stepwith cerium oxide abrasive particles or colloidal silica abrasive grainsusing a double-side polishing apparatus. Then, the glass substrate wassubjected to a surface treatment with hydrosilicofluoric acid of a lowconcentration. The surface roughness of the surface of the glasssubstrate provided through the treatment was measured with an atomicforce microscope, and the root mean square roughness (Rms) was 0.15 nm.

The surface shapes (surface state, flatness) of areas of 148 mm×148 mmat the top and bottom sides of the glass substrate and TTV (variation inthickness) were measured with a wavelength shift interferometer using alaser wavelength modulation. As a result, the flatnesses of the top andbottom sides of the glass substrate were 290 nm (convex shape). Theresults of measuring the surface shape (flatness) of the surfaces of theglass substrate was saved in a computer as height information withrespect to a reference surface provided for each measuring point, andwas compared with a reference value of 50 nm (convex shape) of theflatness of the top surface and the a reference value of 50 nm of theflatness of the bottom surface needed for the glass substrate, and adifference between the comparison results (required amount of removal)was computed by the computer.

Then, the processing conditions for the local surface processingaccording to the required amount of removal were set for each area witha processing spot shape in the surface of the glass substrate. A dummysubstrate was spot-processed in advance in the same manner as in theactual processing without being moved for a given period of time, theshape of the dummy substrate was measured with the same measuring deviceas used to measure the shapes of the top and bottom surfaces, and thevolume of spot processing per unit time was measured. Then, The scanningspeed for raster scanning of the glass substrate was decided accordingto the required amount of removal obtained from the spot information andthe information on the surface shape of the glass substrate.

The surface shape was adjusted by performing a local surface treatmentby magneto rheological finishing (MRF) according to the processingconditions to be set, using a substrate finishing device with magneticfluid, in such a way that the flatnesses of the top and bottom sides ofthe glass substrate would not become more than the reference valuedescribed above. It is noted that the magnetic viscoelastic fluid usedfor this treatment contained an iron component, and the polishing slurrywas an aqueous alkali solution+abrasives (about 2 wt %) with theabrasive being cerium oxide. Thereafter, the glass substrate wasimmersed in a cleaning bath (temperature of about 25° C.) containingaqueous hydrochloric acid with a concentration of about 10% for about 10minutes, and then rinsed with pure water and dried by isopropyl alcohol.

The surface shape (surface state, flatness) of the obtained glasssubstrate surface was measured; the flatnesses of the top and bottomsides were about 40 to 50 nm. Further, the surface roughness of thesurface of the glass substrate in an area of 1 μm×1 μm at an arbitrarylocation in the transfer-pattern forming area (132 mm×132 mm) wasmeasured with an atomic force microscope, showing the root mean squareroughness (Rms) of 0.37 nm, which rougher than the surface roughnessbefore the local surface treatment with MRF.

Therefore, both sides were polished with a double-side polishingapparatus under the polishing conditions to keep or improve the surfaceshape of the surfaces of the glass substrate. This finish polishing wasperformed under the following polishing conditions:

working fluid: aqueous alkaline solution (NaOH)+abrasive (concentration:about 2 wt %)

abrasive: colloidal silica, average particle size: about 70 nm

polishing plate rotational speed: about 1 to 50 rpm

processing pressure: about 0.1 to 10 kPa

polishing time: about 1 to 10 minutes

Then, the glass substrate was rinsed with an aqueous alkaline solution(NaOH) to provide a mask blank substrate 10 of EUV exposure.

The flatnesses and surface roughnesses of the top and bottom sides ofthe provided mask blank substrate 10 were measured, and the flatnessesof the top and bottom sides were about 40 nm, which kept or improved thesurface states before the double-side polishing and it is preferable.Further, an area of 1 μm×1 μm at an arbitrary location in thetransfer-pattern forming area (132 mm×132 mm) in the provided mask blanksubstrate 10 was measured with an atomic force microscope, and thesurface roughness was 0.13 nm in terms of the root mean square roughness(Rms), and the maximum height (Rmax) was 1.2 nm.

The local processing method for the mask blank substrate 10 according tothe invention is not limited to the aforementioned magnetic viscoelasticfluid polishing method. The processing method may use gas cluster ionbeams (GCIB) or local plasma.

Next, a TaBN film was deposited on the main surface of theaforementioned mask blank substrate 10 by DC magnetron sputtering. Witha TaB target set to face the main surface of the mask blank substrate,reactive sputtering was performed under Ar+N₂ gas atmosphere. Theelemental composition of the TaBN film was measured by Rutherfordbackscattering spectrometry, resulting in Ta: 80 atomic %, B: 10 atomic%, and N: 10 atomic %. The thickness of the TaBN film was 150 nm.Measurement of the crystal structure of the TaBN film showed that thecrystal structure was an amorphous structure.

Then, the surface of the TaBN film was subjected to ultra-precisionpolishing using a single-side polishing apparatus. This ultra-precisionpolishing was performed under the following polishing conditions:

working fluid: aqueous alkaline solution (NaOH)+abrasive (averageabrasive grain of 50 nm of colloidal silica, concentration: 5 wt %)

processing pressure: 50 g/cm²

polishing time: about 1 to 10 minutes

Next, the surface of the TaBN film was rinsed for 428 seconds with anaqueous solution of hydrofluoric acid (HF: concentration of 0.2 wt %),providing a mask blank substrate for EUV exposure.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the surface of the TaBN film of the maskblank substrate 10 for EUV exposure provided as Example 1 was measuredwith an atomic force microscope; the surface roughness was 0.085 nm interms of the root mean square roughness (Rms), and the maximum height(Rmax) was 1.1 nm. The results of the power spectrum analysis on theTaBN film surface of the provided mask blank substrate 10 for EUVexposure are shown by “+” in the graphs in FIGS. 7 and 8.

As shown in FIGS. 7 and 8, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the surface of the TaBN film ofExample 1 with an atomic force microscope, at a spatial frequency of notless than 1 μm⁻¹ and not more than 10 μm⁻¹, had a maximum value of 7.73nm⁴ and a minimum value of 2.94 nm⁴. In addition, the power spectrumdensity at a spatial frequency of not less than 10 μm⁻¹ and not morethan 100 μm⁻¹ had a maximum value of 3.47 nm⁴ and a minimum value of1.86 nm⁴. As illustrated in these figures, the power spectrum densitiesof the surface of the TaBN film of Example 1 at a spatial frequency ofnot less than 1 μm⁻¹ and at a spatial frequency of not less than 1 μm⁻¹and not more than 10 μm⁻¹ were not more than 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of the TaBNfilm of Example 1 was performed under the inspection sensitivityconditions that permit detection of defects of not more than 20 nm interms of SEVD (Sphere Equivalent Volume Diameter) using thehigh-sensitivity defect inspection apparatus (“Teron 600 series” ofKLA-Tencor Corp.) with an inspection light source wavelength of 193 nm.As a result, the number of defects detected including false defects wasa total of 18,789, showing that the false defects was significantlysuppressed compared with the conventional number (more than 100,000) ofdetected defects. The total number of detected defects of about 18,789can ensure that presence or absence of critical defects such as aforeign matter or scratches is easily inspected. The SEVD can becalculated from SEVD=2(3S/4πh)^(1/3) where S represents the area of adefect and h represents the height of the defect. (The same is true ofthe following Examples and Comparative Examples.) The defect area S andthe defect height h can be measured by an atomic force microscopy (AFM).

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe TaBN film of Example 1 was performed under the best inspectionsensitivity conditions using the high-sensitivity defect inspectionapparatus (“MAGICS M7360” of Lasertec Corp.) with an inspection lightsource wavelength of 266 nm, resulting in that the total number ofdetected defects in each detection was less than 100,000, which enablesinspection of critical defects.

<Fabrication of Substrate with Multilayer Reflective Film>

The substrate with a multilayer reflective film 20 was fabricated byforming the multilayer reflective film 21 having alternate lamination ofhigh refractive index layers and low refractive index layers, and theprotective film 22 by ion beam sputtering, on the surface of the TaBNfilm of the above-described mask blank substrate 10 for EUV exposure.

For the multilayer reflective film 21, 40 pairs of Si and Mo films, eachpair having a Si film with a thickness of 4.2 nm and a Mo film with athickness of 2.8 nm (total film thickness of 280 nm), were deposited.Further, the protective film 22 of Ru with a thickness of 2.5 nm wasdeposited on the surface of the multilayer reflective film 21. It isnoted that the multilayer reflective film 21 was deposited by ion beamsputtering in such a way that the incident angle of sputtered particlesfor the Si film to the normal line of the main surface of the substratewas 5 degrees, and the incident angle of sputtered particles for the Mofilms thereto was 65 degrees.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.141 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.49 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 14.4 nm⁴and a minimum value of 0.13 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 7.64 nm⁴ and a minimum valueof 0.09 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 1 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 19,132, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects. Inaddition, the reflectance for EUV light was measured, resulting in goodresults of 65%.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe multilayer reflective film of Example 1 was performed using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm and thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. As a result, the total number of detecteddefects in each detection was less than 100,000, which enablesinspection of critical defects. It is noted that defect inspection wasperformed under the best inspection sensitivity conditions using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm, and defectinspection was performed using the high-sensitivity defect inspectionapparatus with an inspection light source wavelength of 13.5 nm underthe inspection sensitivity conditions that permit detection of defectswith the SEVD of not more than 20 nm.

Fiducial marks for managing coordinates were formed on the protectivefilm 22 and the multilayer reflective film 21 of the substrate with amultilayer reflective film 20 of Example 1, at four locations outsidethe transfer-pattern forming area (132 mm×132 mm) by a focused ion beam.

<Fabrication of Reflective Mask Blank for EUV Exposure>

The back-side conductive film 23 was formed by DC magnetron sputtering,on the bottom side of the aforementioned substrate with a multilayerreflective film 20 where the multilayer reflective film 21 was notformed. For the back-side conductive film 23, reactive sputtering wasperformed on the back-side conductive film 23, with a Cr target set toface the bottom side of the substrate with a multilayer reflective film20, under an Ar+N₂ (Ar:N₂=90%: 10%) gas atmosphere. The elementalcomposition of the back-side conductive film 23 was measured byRutherford backscattering spectrometry. The results were Cr: 90 atomic %and N: 10 atomic %. The thickness of the back-side conductive film 23was 20 nm.

Further, the absorber film 24 comprising a TaBN film was deposited by DCmagnetron sputtering, on the surface of the protective film 22 of theaforementioned substrate with a multilayer reflective film 20, therebyfabricating the reflective mask blank 30. For the absorber film 24,reactive sputtering was performed on the absorber film 24 with a TaBtarget (Ta:B=80:20) set to face the absorber film 24 of the substratewith a multilayer reflective film 20, under Xe+N₂ gas (Xe:N₂=90%:10%)atmosphere. The elemental composition of the absorber film 24 wasmeasured by Rutherford backscattering spectrometry. The results were Ta:80 atomic %, B: 10 atomic %, and N: 10 atomic %. In addition, thethickness of the absorber film 24 was 65 nm. Measurement of the crystalstructure of the absorber film 24 showed that the crystal structure wasan amorphous structure.

<Fabrication of Reflective Mask>

A resist was coated on the surface of the aforementioned absorber film24 by spin coating, followed by heating and cooling processes, forforming a resist film 25 with a thickness of 150 nm. Then, a resistpattern was formed through desired drawing and developing. With theresist pattern used as a mask, the TaBN film serving as the absorberfilm 24 was patterned by dry etching with Cl₂+He gas, forming theabsorber pattern 27 on the protective film 22. Then, the resist film 25was removed, and the resultant structure was chemically cleaned in theabove-described manner to fabricate the reflective mask 40. In thedrawing process, drawing data was corrected in such a way that theabsorber pattern 27 was placed at a location where critical defects arepresent, based on defect data created based on the fiducial marks, anddata on a pattern to be transferred (circuit pattern), thus fabricatingthe reflective mask 40. Defection inspection of the provided reflectivemask 40 was performed using the high-sensitivity defect inspectionapparatus (“Teron 600 series” of KLA-Tencor Corp.), but defects were notobserved.

Example 2

<Fabrication of Mask Blank Substrate>

For a mask blank substrate 10, a SiO₂—TiO₂ glass substrate with a sizeof 152.4 mm×152.4 mm and a thickness of 6.35 mm was prepared as the maskblank substrate 10 for EUV exposure, and the top and bottom sides of theglass substrate were subjected to processes from polishing with thedouble-side polishing apparatus to the local surface treatment bymagnetic viscoelastic fluid polishing, with the same manner as inExample 1.

Thereafter, noncontact polishing of the top and bottom sides of theglass substrate was performed as finish polishing in the local surfacetreatment. In Example 2, EEM (Elastic Emission Machining) was performedas the non-contact polishing. The EEM was performed under the followingprocessing conditions.

working fluid (first stage): aqueous alkaline solution (NaOH)+finepowder particles (concentration: 5 wt %)

working fluid (second stage): pure water

fine powder particles: colloidal silica, average particle size: about100 nm

rotational body: polyurethane roll

rotational speed of the rotating body: 10 to 300 rpm

rotational speed of the work holder: 10 to 100 rpm

polishing time: 5 to 30 minutes

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for EUV exposure provided by Example 2 was measured with anatomic force microscope; the root mean square roughness (Rms) was 0.10nm, and the maximum height (Rmax) was 1.0 nm. The results of the powerspectrum analysis on the main surface of the provided mask blanksubstrate 10 for EUV exposure are shown by “▴” in the graphs in FIGS. 7and 8.

As shown in FIGS. 7 and 8, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the main surface of the mask blanksubstrate 10 for EUV exposure of Example 2 with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹, had a maximum value of 7.40 nm⁴ and a minimum value of2.16 nm⁴. In addition, the power spectrum density at a spatial frequencyof not less than 10 μm⁻¹ and not more than 100 μm⁻¹ had a maximum valueof 3.32 nm⁴ and a minimum value of 2.13 nm⁴. As illustrated in thesefigures, the power spectrum densities of the surface of the main surfaceof the mask blank substrate of Example 2 at a spatial frequency of notless than 1 μm⁻¹ and at a spatial frequency of not less than 1 μm⁻¹ andnot more than 10 μm⁻¹ were not more than 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for EUV exposure of Example 2 was performedunder the inspection sensitivity conditions that permit detection ofdefects of not more than 20 nm in terms of SEVD (Sphere EquivalentVolume Diameter) using the high-sensitivity defect inspection apparatus(“Teron 600 series” of KLA-Tencor Corp.) with an inspection light sourcewavelength of 193 nm. As a result, the number of defects detectedincluding false defects was a total of 29,129, showing that the falsedefects was significantly suppressed compared with the conventionalnumber (more than 100,000) of detected defects. The total number ofdetected defects of about 29,129 can ensure that presence or absence ofcritical defects such as a foreign matter or scratches is easilyinspected.

Further, defect inspection of an area of 132 mm×132 mm at the mask blanksubstrate 10 for EUV exposure of Example 2 was performed under the bestinspection sensitivity conditions using the high-sensitivity defectinspection apparatus (“MAGICS M7360” of Lasertec Corp.) with aninspection light source wavelength of 266 nm, resulting in that thetotal number of detected defects in each detection was less than100,000, which enables inspection of critical defects.

The multilayer reflective film 21 with a thickness 280 nm having Sifilms and Mo films alternately laminated, which is the same as Example1, was formed on the main surface of the aforementioned mask blanksubstrate 10 of the EUV exposure, and the protective film 22 of Ru witha thickness of 2.5 nm was deposited on the surface of the multilayerreflective film 21. The ion beam sputtering conditions for themultilayer reflective film 21 were the same as those in Example 1.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.143 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.50 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 17.4 nm⁴and a minimum value of 0.14 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 8.62 nm⁴ and a minimum valueof 0.11 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 2 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 30,011, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe multilayer reflective film of Example 2 was performed using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm and thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. As a result, the total number of detecteddefects in each detection was less than 100,000, which enablesinspection of critical defects.

The reflective mask blank 30 and the reflective mask 40 were fabricatedin the same manner as done in the above-described Example 1. Defectinspection of the obtained reflective mask 40 was performed using thehigh-sensitivity defect inspection apparatus (KLA-Tencor Corp. “Teron600 Series”); no defects were observed. It is noted that defectinspection was performed under the best inspection sensitivityconditions using the high-sensitivity defect inspection apparatus(“MAGICS M7360” of Lasertec Corp.) with an inspection light sourcewavelength of 266 nm, and defect inspection was performed using thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm under the inspection sensitivity conditionsthat permit detection of defects with the SEVD of not more than 20 nm.

Example 3

<Fabrication of Mask Blank Substrate>

In this Example 3, a SiO₂—TiO₂ glass substrate with a size of 152.4mm×152.4 mm and a thickness of 6.35 mm was prepared as the mask blanksubstrate 10 for EUV exposure, which is the same as Examples 1 and 2,and the mask blank substrate 10 for EUV exposure was fabricated throughsubstantially the same processes as done in Example 2. It is noted that,in Example 3, EEM processing at the second stage using pure water as theworking fluid was omitted in finish polishing in the local surfacetreatment in Example 2.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for EUV exposure provided by Example 3 was measured with anatomic force microscope; the root mean square roughness (Rms) was 0.11nm, and the maximum height (Rmax) was 1.2 nm. The results of the powerspectrum analysis on the main surface of the provided mask blanksubstrate 10 for EUV exposure are shown by “♦” in the graphs in FIGS. 7and 8.

As shown in FIGS. 7 and 8, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the main surface of the mask blanksubstrate 10 for EUV exposure of Example 3 with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹, had a maximum value of 10.00 nm⁴ and a minimum value of3.47 nm⁴. In addition, the power spectrum density at a spatial frequencyof not less than 10 μm⁻¹ and not more than 100 μm⁻¹ had a maximum valueof 3.96 nm⁴ and a minimum value of 2.56 nm⁴. As illustrated in thesefigures, the power spectrum densities of the surface of the main surfaceof the mask blank substrate of Example 3 at a spatial frequency of notless than 1 μm⁻¹ and at a spatial frequency of not less than 1 μm⁻¹ andnot more than 10 μm⁻¹ were not more than 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for EUV exposure of Example 3 was performedunder the inspection sensitivity conditions that permit detection ofdefects of not more than 20 nm in terms of SEVD (Sphere EquivalentVolume Diameter) using the high-sensitivity defect inspection apparatus(“Teron 600 series” of KLA-Tencor Corp.) with an inspection light sourcewavelength of 193 nm. As a result, the number of defects detectedincluding false defects was a total of 36,469, showing that the falsedefects was significantly suppressed compared with the conventionalnumber (more than 100,000) of detected defects. The total number ofdetected defects of about 36,469 can ensure that presence or absence ofcritical defects such as a foreign matter or scratches is easilyinspected.

Further, defect inspection of an area of 132 mm×132 mm at the mask blanksubstrate 10 for EUV exposure of Example 3 was performed under the bestinspection sensitivity conditions using the high-sensitivity defectinspection apparatus (“MAGICS M7360” of Lasertec Corp.) with aninspection light source wavelength of 266 nm, resulting in that thetotal number of detected defects in each detection was less than100,000, which enables inspection of critical defects.

<Fabrication of Substrate with Multilayer Reflective Film>

The multilayer reflective film 21 with a thickness 280 nm having Sifilms and Mo films alternately laminated, which is the same as Example1, was formed on the main surface of the aforementioned mask blanksubstrate 10 of the EUV exposure, and the protective film 22 of Ru witha thickness of 2.5 nm was deposited on the surface of the multilayerreflective film 21. The ion beam sputtering conditions for themultilayer reflective film 21 were the same as those in Example 1.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.146 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.50 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 17.9 nm⁴and a minimum value of 0.16 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 8.76 nm⁴ and a minimum valueof 0.11 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 3 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 38,856, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe multilayer reflective film of Example 3 was performed using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm and thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. As a result, the total number of detecteddefects in each detection was less than 100,000, which enablesinspection of critical defects. It is noted that defect inspection wasperformed under the best inspection sensitivity conditions using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm, and defectinspection was performed using the high-sensitivity defect inspectionapparatus with an inspection light source wavelength of 13.5 nm underthe inspection sensitivity conditions that permit detection of defectswith the SEVD of not more than 20 nm.

The reflective mask blank 30 and the reflective mask 40 were fabricatedin the same manner as done in the above-described Example 1. Defectinspection of the obtained reflective mask 40 was performed using thehigh-sensitivity defect inspection apparatus (KLA-Tencor Corp. “Teron600 Series”); no defects were observed.

The non-contact polishing as finish polishing of the local surfacetreatment in Examples 2 and 3 are not limited to the above-describedEEM. For example, it is possible to apply float polish orcatalyst-referred etching. In any case, finish polishing of the mainsurface of the glass substrate is preferably non-contact polishing usingwater or pure water.

Comparative Example 1

<Fabrication of Mask Blank Substrate>

For Comparative Example 1, a SiO₂—TiO₂ glass substrate with a size of152.4 mm×152.4 mm and a thickness of 6.35 mm was prepared as the maskblank substrate 10 for EUV exposure, which is the same as Example 2.

In Comparative Example 1, unlike in Example 2, as fine polishing in thelocal surface treatment, ultra-precision polishing was performed withsingle-side polishing apparatus using a polishing slurry comprisingcolloidal silica (average particle size of 50 nm, concentration of 5 wt%) adjusted to acidity with a pH of 0.5 to 4, and then rinsing withsodium hydroxide (NaOH) having a concentration of 0.1 wt % was performedfor a rinsing time of 300 seconds.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for EUV exposure provided by Comparative Example 1 wasmeasured with an atomic force microscope; the root mean square roughness(Rms) was 0.11 nm, and the maximum height (Rmax) was 1.0 nm. The resultsof the power spectrum analysis on the main surface of the provided maskblank substrate 10 for EUV exposure are shown by “●” in the graphs inFIGS. 7 and 9.

As shown in FIGS. 7 and 9, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the main surface of the mask blanksubstrate 10 for EUV exposure of Comparative Example 1 with an atomicforce microscope, at a spatial frequency of not less than 1 μm⁻¹ and notmore than 10 μm⁻¹, had a maximum value of 14.81 nm⁴ and a minimum valueof 3.87 nm⁴. As illustrated in these figures, the maximum values of thepower spectrum densities of the surface of the main surface of the maskblank substrate of Comparative Example 1 at a spatial frequency of notless than 1 μm⁻¹ and at a spatial frequency of not less than 1 μm⁻¹ andnot more than 10 μm⁻¹ exceeded 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for EUV exposure of Comparative Example 1 wasperformed under the inspection sensitivity conditions that permitdetection of defects of not more than 20 nm in terms of SEVD (SphereEquivalent Volume Diameter) using the high-sensitivity defect inspectionapparatus (“Teron 600 series” of KLA-Tencor Corp.) with an inspectionlight source wavelength of 193 nm. As a result, the total number ofdefects detected including false defects exceeded 100,000, whichdisables inspection of the presence or absence of critical defects suchas a foreign matter or scratches.

<Fabrication of Substrate with Multilayer Reflective Film>

The multilayer reflective film 21 with a thickness 280 nm having Sifilms and Mo films alternately laminated, which is the same as Example1, was formed on the main surface of the aforementioned mask blanksubstrate 10 of the EUV exposure, and the protective film 22 of Ru witha thickness of 2.5 nm was deposited on the surface of the multilayerreflective film 21. The ion beam sputtering conditions for themultilayer reflective film 21 were the same as those in Example 1.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.165 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.61 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ exceeded 20 nm⁴, and had a maximum value of 22.8 nm⁴ and aminimum value of 0.19 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ exceeded 9nm⁴, and had a maximum value of 9.53 nm⁴ and a minimum value of 0.12nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofComparative Example 1 was performed under the inspection sensitivityconditions that permit detection of defects of not more than 20 nm interms of SEVD (Sphere Equivalent Volume Diameter) using thehigh-sensitivity defect inspection apparatus (“Teron 600 series” ofKLA-Tencor Corp.) with an inspection light source wavelength of 193 nm.As a result, the total number of defects detected including falsedefects exceeded 100,000, which disables inspection of the presence orabsence of critical defects such as a foreign matter or scratches.

The same is true of the results of defect inspection of an area of 132mm×132 mm at the surface of the protective film of the multilayerreflective film of Comparative Example 1 performed under the inspectionsensitivity conditions that permit detection of defects of not more than20 nm in terms of SEVD (Sphere Equivalent Volume Diameter) using thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. The results show that the total number ofdefects detected including false defects exceeded 100,000, whichdisables inspection of the presence or absence of critical defects. Thereflective mask blank 30 and the reflective mask 40 were fabricated inthe same manner as done in the above-described Example 1. Defectinspection of the obtained reflective mask 40 was performed using thehigh-sensitivity defect inspection apparatus (KLA-Tencor Corp. “Teron600 Series”); although several tens of defects were observed, defectcorrection was performed with a defect correcting device to provide areflective mask.

Comparative Example 2

In Comparative Example 2, a SiO₂—TiO₂ glass substrate with a size of152.4 mm×152.4 mm and a thickness of 6.35 mm was prepared as the maskblank substrate 10 for EUV exposure, which is the same as Example 2.

In Comparative Example 2, unlike in Example 2, as fine polishing in thelocal surface treatment, ultra-precision polishing was performed withsingle-side polishing apparatus using a polishing slurry comprisingcolloidal silica (average particle size of 50 nm, concentration of 5 wt%) adjusted to alkalinity with a pH of 10, and then rinsing withhydrofluoric acid (HF) with a concentration of 0.2 wt % was performedfor a rinsing time of 428 seconds.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for EUV exposure provided by Comparative Example 2 wasmeasured with an atomic force microscope; the root mean square roughness(Rms) was 0.15 nm, and the maximum height (Rmax) was 1.2 nm. The resultsof the power spectrum analysis on the main surface of the provided maskblank substrate 10 for EUV exposure are shown by “▪” in the graphs inFIGS. 7 and 9.

As shown in FIGS. 7 and 9, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the main surface of the mask blanksubstrate 10 for EUV exposure of Comparative Example 2 with an atomicforce microscope, at a spatial frequency of not less than 1 μm⁻¹ and notmore than 10 μm⁻¹, had a maximum value of 11.65 nm⁴ and a minimum valueof 5.16 nm⁴. In addition, the power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ had amaximum value of 7.20 nm⁴ and a minimum value of 4.08 nm⁴. Asillustrated in these figures, the maximum values of the power spectrumdensities of the surface of the main surface of the mask blank substrateof Comparative Example 2 at a spatial frequency of not less than 1 μm⁻¹and at a spatial frequency of not less than 1 μm⁻¹ and not more than 10μm⁻¹ exceeded 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for EUV exposure of Comparative Example 2 wasperformed under the inspection sensitivity conditions that permitdetection of defects of not more than 20 nm in terms of SEVD (SphereEquivalent Volume Diameter) using the high-sensitivity defect inspectionapparatus (“Teron 600 series” of KLA-Tencor Corp.) with an inspectionlight source wavelength of 193 nm. As a result, the total number ofdefects detected including false defects exceeded 100,000, whichdisables inspection of the presence or absence of critical defects suchas a foreign matter or scratches.

<Fabrication of Substrate with Multilayer Reflective Film>

The multilayer reflective film 21 with a thickness 280 nm having Sifilms and Mo films alternately laminated, which is the same as Example1, was formed on the main surface of the aforementioned mask blanksubstrate 10 of the EUV exposure, and the protective film 22 of Ru witha thickness of 2.5 nm was deposited on the surface of the multilayerreflective film 21. The ion beam sputtering conditions for themultilayer reflective film 21 were the same as those in Example 1.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.173 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.56 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ exceeded 20 nm⁴, and had a maximum value of 25.2 nm⁴ and aminimum value of 0.27 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ exceeded 9nm⁴, and had a maximum value of 9.60 nm⁴ and a minimum value of 0.15nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofComparative Example 2 was performed under the inspection sensitivityconditions that permit detection of defects of not more than 20 nm interms of SEVD (Sphere Equivalent Volume Diameter) using thehigh-sensitivity defect inspection apparatus (“Teron 600 series” ofKLA-Tencor Corp.) with an inspection light source wavelength of 193 nm.As a result, the total number of defects detected including falsedefects exceeded 100,000, which disables inspection of the presence orabsence of critical defects such as a foreign matter or scratches.

The same is true of the results of defect inspection of an area of 132mm×132 mm at the surface of the protective film of the multilayerreflective film of Comparative Example 2 using the high-sensitivitydefect inspection apparatus with an inspection light source wavelengthof 13.5 nm; the total number of defects detected including false defectsin each detection exceeded 100,000, which disables inspection of thepresence or absence of critical defects. For the high-sensitivity defectinspection apparatus with the inspection light source wavelength of 13.5nm, defect inspection was performed under the inspection sensitivityconditions that would permit detection of defects with the SEVD of notmore than 20 nm. The reflective mask blank 30 and the reflective mask 40were fabricated in the same manner as done in the above-describedExample 1. Defect inspection of the obtained reflective mask 40 wasperformed using the high-sensitivity defect inspection apparatus(KLA-Tencor Corp. “Teron 600 Series”); although several tens of defectswere observed, defect correction was performed with a defect correctingdevice to provide a reflective mask.

Example 4

Next, Example 4 for the mask blank substrate, the transmissive maskblank, and the transmissive mask for ArF excimer laser exposureaccording to the invention is described.

<Fabrication of Mask Blank Substrate>

In Example 4, a synthetic quartz glass substrate of the same size asthose in Examples 1 to 3 were used, except for which the mask blanksubstrate 10 for ArF excimer laser exposure was fabricated throughprocesses similar to those in the above-described in <Fabrication ofMask Blank Substrate> of Example 2.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for ArF excimer laser exposure provided by Example 4 wasmeasured with an atomic force microscope; the root mean square roughness(Rms) was 0.11 nm, and the maximum height (Rmax) was 0.93 nm. Theresults of the power spectrum analysis on the main surface of theprovided mask blank substrate 10 for ArF excimer laser exposure areshown by “*” in the graphs in FIGS. 7 and 8.

As shown in FIGS. 7 and 8, the power spectrum density, obtained bymeasuring an area of 1 μm×1 μm of the main surface of the mask blanksubstrate 10 for ArF excimer laser exposure of Example 4 with an atomicforce microscope, at a spatial frequency of not less than 1 μm⁻¹ and notmore than 10 μm⁻¹, had a maximum value of 8.72 nm⁴ and a minimum valueof 2.03 nm⁴. As illustrated in these figures, the power spectrumdensities of the surface of the main surface of the mask blank substrateof Example 4 at a spatial frequency of not less than 1 μm⁻¹ and at aspatial frequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹ werenot more than 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for ArF excimer laser exposure of Example 4 wasperformed using the high-sensitivity defect inspection apparatus (“Teron600 series” of KLA-Tencor Corp.) with an inspection light sourcewavelength of 193 nm. As a result, the number of defects detectedincluding false defects was a total of 31,056, showing that the falsedefects was significantly suppressed compared with the conventionalnumber (more than 100,000) of detected defects. The total number ofdetected defects of about 31,056 can ensure that presence or absence ofcritical defects such as a foreign matter or scratches is easilyinspected.

<Fabrication of Transmissive Mask Blank>

The above-described mask blank substrate 10 for ArF excimer laserexposure was set into a DC magnetron sputtering apparatus, and a TaNlayer was deposited on the main surface of the mask blank substrate 10.A gas mixture of Xe+N₂ was supplied into the DC magnetron sputteringapparatus to perform sputtering using a Ta target. As a result, a TaNlayer with a thickness of 44.9 nm was deposited on the main surface ofthe mask blank substrate 10.

Then, the gas in the DC magnetron sputtering apparatus was replaced witha mixture gas of Ar+O₂ to perform sputtering using a Ta target again. Asa result, a TaO layer with a thickness of 13 nm was deposited on thesurface of the TaN layer, providing a transmissive mask blank (binarymask blank) with a 2-layered light shielding function film 51 formed onthe mask blank substrate 10. The crystal structure of the lightshielding function film 51 was measured by X-ray diffractometer (XRD),and it was an amorphous structure.

Defect inspection of an area of 132 mm×132 mm at the light shieldingfunction film 51 on the mask blank substrate 10 of Example 4 wasperformed under the inspection sensitivity conditions that permitdetection of defects of not more than 20 nm in terms of SEVD (SphereEquivalent Volume Diameter) using the high-sensitivity defect inspectionapparatus (“Teron 600 series” of KLA-Tencor Corp.) with an inspectionlight source wavelength of 193 nm. As a result, the number of defectsdetected including false defects was a total of 33,121, showing that thefalse defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects. The totalnumber of detected defects of about 33,121 can ensure that presence orabsence of critical defects such as a foreign matter or scratches iseasily inspected.

<Fabrication of Transmissive Mask>

A resist was coated on the surface of the aforementioned light shieldingfunction film 51 by spin coating, followed by heating and coolingprocesses, for forming a resist film 25 with a thickness of 150 nm.Then, a resist pattern was formed through desired drawing anddeveloping. With the resist pattern used as a mask, the TaO layer waspatterned by dry etching with fluorinated (CHF₃) gas, then the TaN layerwas patterned by dry etching with a chlorine (Cl₂) gas, forming thelight-shielding-function film pattern 61 on the mask blank substrate 10.Thereafter, the resist film 25 was removed, and the resultant structurewas chemically cleaned in the above-described manner to fabricate thetransmissive mask 60. Defection inspection of the provided transmissivemask 60 was performed using the high-sensitivity defect inspectionapparatus (“Teron 600 series” of KLA-Tencor Corp.), resulting inobservation of no defects.

Example 5

A SiO₂—TiO₂ glass substrate with a size of 152.4 mm×152.4 mm and athickness of 6.35 mm was prepared as the mask blank substrate 10 for EUVexposure, and the top and bottom sides of the glass substrate weresubjected to processes from polishing with the double-side polishingapparatus to the local surface treatment by magnetic viscoelastic fluidpolishing, with the same manner as in Example 1.

Thereafter, as final polishing of the local surface treatment,double-sided touch polishing using colloidal silica abrasive was carriedout for the purpose of improving the surface roughness, and then asurface treatment by catalyst-referred etching (CARE) was carried outunder the following processing conditions.

working fluid: pure water

catalyst: platinum

rotational speed of the substrate: 10.3 rotations/min

rotational speed of the catalyst: 10 rotations/min

processing time: 50 minutes

processing pressure: 250 hPa

Then, after scrubbing the end faces of the glass substrate, thesubstrate was immersed in a cleaning tank containing aqua regia(temperature of about 65° C.) for about 10 minutes, after which thesubstrate was rinsed with pure water, followed by drying. It is notedthat washing with aqua regia was performed multiple times until the topand bottom sides of the glass substrate were free of the residue ofplatinum serving as the catalyst.

An area of 1 μm×1 μm at an arbitrary location in the transfer-patternforming area (132 mm×132 mm) on the main surface of the mask blanksubstrate 10 for EUV exposure provided by Example 5 was measured with anatomic force microscope; the root mean square roughness (Rms) was 0.040nm, and the maximum height (Rmax) was 0.40 nm. The results of the powerspectrum analysis on the main surface of the provided mask blanksubstrate 10 for EUV exposure are shown by “●” in the graphs in FIG. 10.

As shown in FIG. 10, the power spectrum density, obtained by measuringan area of 1 μm×1 μm of the main surface of the mask blank substrate 10for EUV exposure of Example 5 with an atomic force microscope, at aspatial frequency of not less than 1 μm⁻¹ and not more than 10 μm⁻¹, hada maximum value of 5.29 nm⁴ and a minimum value of 1.15 nm⁴. Inaddition, the power spectrum density at a spatial frequency of not lessthan 10 μm⁻¹ and not more than 100 μm⁻¹ had a maximum value of 1.18 nm⁴and a minimum value of 0.20 nm⁴. As illustrated in these figures, thepower spectrum densities of the surface of the main surface of the maskblank substrate of Example 5 at a spatial frequency of not less than 1μm⁻¹ and at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹ were not more than 10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the main surface of themask blank substrate 10 for EUV exposure of Example 5 was performedunder the inspection sensitivity conditions that permit detection ofdefects of not more than 20 nm in terms of SEVD (Sphere EquivalentVolume Diameter) using the high-sensitivity defect inspection apparatus(“Teron 600 series” of KLA-Tencor Corp.) with an inspection light sourcewavelength of 193 nm. As a result, the number of defects detectedincluding false defects was a total of 370, showing that the falsedefects was significantly suppressed compared with the conventionalnumber (more than 100,000) of detected defects. The total number ofdetected defects of about 370 can ensure that presence or absence ofcritical defects such as a foreign matter or scratches is easilyinspected.

Further, defect inspection of an area of 132 mm×132 mm at the mask blanksubstrate 10 for EUV exposure of Example 5 was performed under the bestinspection sensitivity conditions using the high-sensitivity defectinspection apparatus (“MAGICS M7360” of Lasertec Corp.) with aninspection light source wavelength of 266 nm, resulting in that thetotal number of detected defects in each detection was less than100,000, which enables inspection of critical defects.

<Fabrication of Substrate with Multilayer Reflective Film>

The multilayer reflective film 21 with a thickness 280 nm having Sifilms and Mo films alternately laminated, which is the same as Example1, was formed on the main surface of the aforementioned mask blanksubstrate 10 of the EUV exposure, and the protective film 22 of Ru witha thickness of 2.5 nm was deposited on the surface of the multilayerreflective film 21. The ion beam sputtering conditions for themultilayer reflective film 21 were the same as those in Example 1.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.135 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.27 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 15.5 nm⁴and a minimum value of 0.09 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 7.51 nm⁴ and a minimum valueof 0.10 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 5 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 13,512, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe multilayer reflective film of Example 5 was performed using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm and thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. As a result, the total number of detecteddefects in each detection was less than 100,000, which enablesinspection of critical defects. It is noted that defect inspection wasperformed under the best inspection sensitivity conditions using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm, and defectinspection was performed using the high-sensitivity defect inspectionapparatus with an inspection light source wavelength of 13.5 nm underthe inspection sensitivity conditions that permit detection of defectswith the SEVD of not more than 20 nm.

The reflective mask blank 30 and the reflective mask 40 were fabricatedin the same manner as done in the above-described Example 1. Defectinspection of the obtained reflective mask 40 was performed using thehigh-sensitivity defect inspection apparatus (KLA-Tencor Corp. “Teron600 Series”); no defects were observed.

Example 6

A substrate with a multilayer reflective film was fabricated with thesame manner as the above-described Example 5, except deposition wascarried out by ion beam sputtering with the deposition conditions forthe multilayer reflective film 21 such that the incident angle ofsputtered particles for the Si film to the normal line of the mainsurface of the substrate was 30 degrees, and the incident angle ofsputtered particles for the Mo films thereto was 30 degrees.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.116 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.15 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 9.98 nm⁴and a minimum value of 0.10 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 4.81 nm⁴ and a minimum valueof 0.12 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 6 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 4,758, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe multilayer reflective film of Example 6 was performed using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm and thehigh-sensitivity defect inspection apparatus with an inspection lightsource wavelength of 13.5 nm. As a result, the total number of detecteddefects in each detection was less than 100,000, which enablesinspection of critical defects. It is noted that defect inspection wasperformed under the best inspection sensitivity conditions using thehigh-sensitivity defect inspection apparatus (“MAGICS M7360” of LasertecCorp.) with an inspection light source wavelength of 266 nm, and defectinspection was performed using the high-sensitivity defect inspectionapparatus with an inspection light source wavelength of 13.5 nm underthe inspection sensitivity conditions that permit detection of defectswith the SEVD of not more than 20 nm.

The reflective mask blank 30 and the reflective mask 40 were fabricatedin the same manner as done in the above-described Example 1. Defectinspection of the obtained reflective mask 40 was performed using thehigh-sensitivity defect inspection apparatus (KLA-Tencor Corp. “Teron600 Series”); no defects were observed.

Example 7

The multilayer reflective film 21 and the protective film 22 were formedon the mask blank substrate for EUV exposure according to ComparativeExample 1 with the deposition conditions of the above-described Example6, thereby fabricating a substrate with a multilayer reflective film.

With regard to the surface of the protective film 22 of the providedsubstrate with a multilayer reflective film 20, an area of 1 μm×1 μm atan arbitrary location in the transfer-pattern forming area (132 mm×132mm) was measured with an atomic force microscope; the surface roughnesswas 0.122 nm in terms of the root mean square roughness (Rms), and themaximum height (Rmax) was 1.32 nm. In addition, the power spectrumdensity at a spatial frequency of not less than 1 μm⁻¹ and not more than10 μm⁻¹ was not more than 20 nm⁴, and had a maximum value of 13.3 nm⁴and a minimum value of 0.07 nm⁴. The power spectrum density at a spatialfrequency of not less than 10 μm⁻¹ and not more than 100 μm⁻¹ was notmore than 9 nm⁴, and had a maximum value of 6.74 nm⁴ and a minimum valueof 0.11 nm⁴.

Defect inspection of an area of 132 mm×132 mm at the surface of theprotective film of the substrate with a multilayer reflective film 20 ofExample 7 was performed under the inspection sensitivity conditions thatpermit detection of defects of not more than 20 nm in terms of SEVD(Sphere Equivalent Volume Diameter) using the high-sensitivity defectinspection apparatus (“Teron 600 series” of KLA-Tencor Corp.) with aninspection light source wavelength of 193 nm. As a result, the number ofdefects detected including false defects was a total of 10,218, showingthat the false defects was significantly suppressed compared with theconventional number (more than 100,000) of detected defects. Thereflectance to EUV light was measured, showing a good result of 65%.

Further, defect inspection of an area of 132 mm×132 mm at the surface ofthe protective film of the substrate with a multilayer reflective film20 of Example 7 was performed using the high-sensitivity defectinspection apparatus (“MAGICS M7360” of Lasertec Corp.) with aninspection light source wavelength of 266 nm and the high-sensitivitydefect inspection apparatus with an inspection light source wavelengthof 13.5 nm. As a result, the total number of detected defects in eachdetection was less than 100,000, which enables inspection of criticaldefects. It is noted that defect inspection was performed under the bestinspection sensitivity conditions using the high-sensitivity defectinspection apparatus (“MAGICS M7360” of Lasertec Corp.) with aninspection light source wavelength of 266 nm, and defect inspection wasperformed using the high-sensitivity defect inspection apparatus with aninspection light source wavelength of 13.5 nm under the inspectionsensitivity conditions that permit detection of defects with the SEVD ofnot more than 20 nm.

Further, the reflective mask blank 30 and the reflective mask 40 werefabricated in the same manner as done in the above-described Example 1.Defect inspection of the obtained reflective mask 40 was performed usingthe high-sensitivity defect inspection apparatus (KLA-Tencor Corp.“Teron 600 Series”); no defects were observed.

<Method of Manufacturing Semiconductor Device>

Next, pattern transfer onto resist films on transferred substrates ofsemiconductor substrates with an exposure apparatus using the reflectivemasks and the transmissive masks according to the above-describedExamples 1 to 7 and Comparative Examples 1 and 2 was performed. Afterthat, an interconnection layer was patterned to fabricate semiconductordevices. As a result, when the reflective masks and the transmissivemasks according to the above-described Examples 1 to 7 were used, thesemiconductor devices could be fabricated without pattern defects,whereas when the reflective masks and the transmissive masks accordingto the above-described Comparative Examples 1 and 2 were used, patterndefects occurred, which resulted in defective semiconductor devices.This is because critical defects were buried in false defects and couldnot be detected in defect inspection on the mask blank substrate, thesubstrate with a multilayer reflective film, the reflective mask blank,and reflective mask, which resulted in improper drawing correction andimproper mask correction, so that the reflective mask contained criticaldefects.

In the fabrication of the above-described substrate with a multilayerreflective film 20 and the reflective mask blank 30, the multilayerreflective film 21 and the protective film 22 were deposited on the mainsurface on that side of the mask blank substrate 10 where a transferpattern is formed, followed by forming the back-side conductive film 23on the bottom side opposite to that main surface, but which is notrestrictive. The reflective mask blank 30 may be fabricated by formingthe back-side conductive film 23 on the main surface of the mask blanksubstrate 10 opposite to the side where a transfer pattern is formed,and then depositing the multilayer reflective film 21 and further theprotective film 22 on the main surface on the side where the transferpattern is formed.

DESCRIPTION OF REFERENCE NUMERALS

-   10 a mask blank substrate-   20 a substrate with a multilayer reflective film-   21 a multilayer reflective film-   22 a protective film-   23 a back-side conductive film-   24 an absorber film-   27 an absorber pattern-   30 a reflective mask blank-   40 a reflective mask-   50 a transmissive mask blank-   51 a light shielding function film-   60 a transmissive mask

The invention claimed is:
 1. A transmissive mask blank comprising alight shielding function film to be a transfer pattern on the mainsurface of a mask blank substrate, wherein the surface of the lightshielding function film has a power spectrum density of not more than 10nm⁴, obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹.
 2. The transmissive mask blank according to claim 1,wherein the power spectrum density is not less than 1 nm⁴ and not morethan 10 nm⁴.
 3. The transmissive mask blank according to claim 1,wherein the transmissive mask blank is a binary mask blank with a lightshielding film for shielding exposure light formed on the mask blanksubstrate.
 4. The transmissive mask blank according to claim 1, whereinthe transmissive mask blank is a phase-shift mask blank with a phaseshift film for changing the phase difference of exposure light formed onthe mask blank substrate.
 5. The transmissive mask blank according toclaim 4, wherein the phase-shift mask blank has a structure with a lightshielding film for shielding the exposure light formed on the phaseshift film.
 6. The transmissive mask blank according to claim 1, whereinthe transmissive mask blank is a transmissive mask blank with a resistfilm, the resist film to be a mask for patterning the light shieldingfunction film, and formed on the light shielding function film.
 7. Atransmissive mask comprising a light shielding function film patternprovided on the main surface by patterning the light shielding functionfilm of the transmissive mask blank according to claim
 1. 8. A method ofmanufacturing a semiconductor device, comprising a step of forming atransfer pattern on a transferred substrate by performing a lithographyprocess using an exposure device with the transmissive mask according toclaim
 7. 9. A substrate with a multilayer reflective film for use inlithography, comprising: a multilayer reflective film having a highrefractive index layer and a low refractive index layer alternatelylaminated on a main surface of a mask blank substrate; and, a protectivefilm on the multilayer reflective film, wherein a surface of theprotective film has a root mean square roughness (Rms) of not more than0.15 nm, obtained by measuring an area of 1 μm ×1 μm with an atomicforce microscope, and has a power spectrum density of not more than 20nm⁴ at a spatial frequency of not less than 1 μm⁻¹.
 10. The substratewith a multilayer reflective film according to claim 9, wherein thesurface of the protective film of the substrate with a multilayerreflective film has a power spectrum density of not more than 20 nm⁴,obtained by measuring an area of 1 μm×1 μm with an atomic forcemicroscope, at a spatial frequency of not less than 1 μm⁻¹ and not morethan 10 μm⁻¹.
 11. The substrate with a multilayer reflective filmaccording to claim 9, wherein the surface of the protective film of thesubstrate with a multilayer reflective film has a power spectrum densityof not more than 9 nm⁴, obtained by measuring an area of 1 μm ×1 μm withan atomic force microscope, at a spatial frequency of not less than 10μm⁻¹ and not more than 100 μm⁻¹.
 12. A reflective mask blank comprisingan absorber film to be a transfer pattern on the protective film of thesubstrate with a multilayer reflective film according to claim
 9. 13. Areflective mask comprising an absorber pattern provided on theprotective film by patterning the absorber film of the reflective maskblank according to claim
 12. 14. A method of manufacturing asemiconductor device, comprising forming a transfer pattern on atransferred substrate by performing a lithography process using anexposure device with the reflective mask according to claim 13.